Belgians Florence Lutje Spelberg and Nicolas Mouchart dive into "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, before enjoying a meal inside, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman 

Waitress Valeryia Prusakova brings the dinner in a waterproof box to customers sitting inside "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman 

Waitress Valeryia Prusakova brings the dinner in a waterproof box to customers sitting inside "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman 

Waitress Valeryia Prusakova brings the dinner in a waterproof box to customers sitting inside "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman 

Belgians Florence Lutje Spelberg and Nicolas Mouchart drink champagne while sitting inside "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, before enjoying a meal inside, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman TPX IMAGES OF THE DAY 

Belgians Florence Lutje Spelberg and Nicolas Mouchart drink champagne while sitting inside "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, before enjoying a meal inside, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman TPX IMAGES OF THE DAY 

Belgians Florence Lutje Spelberg and Nicolas Mouchart dive next to "The Pearl", a spheric dining room placed 5 metres underwater in the NEMO33 diving center, one of the world's deepest pools (33 metre/36 yards) built to train professional divers, before enjoying a meal inside, in Brussels, Belgium January 30, 2017. Picture taken January 30, 2017 REUTERS/Yves Herman TPX IMAGES OF THE DAY 

REFILE - CORRECTING BYLINEA video grab taken from SRG footage, shows a split screen displaying VIP trains entering the northern end of the tunnel in Erstfield and southern side of the tunnel in Bodio, during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/SRG/Pool 

A video grab taken from SDR footage, shows a split screen displaying VIP trains entering the northern end of the tunnel in Erstfield and southern side of the tunnel in Bodio, during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/SDR/Pool 

Swiss President Johann Schneider-Ammann cuts the ribbon next to Swiss Federal Railways (SBB) CEO Andreas Meyer and Swiss Transport Minister Doris Leuthard during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann

Swiss President Johann Schneider-Ammann cuts the ribbon next to Swiss Federal Railways (SBB) CEO Andreas Meyer and Swiss Transport Minister Doris Leuthard during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann cuts the ribbon next to Swiss Federal Railways (SBB) CEO Andreas Meyer during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich

Swiss President Johann Schneider-Ammann cuts the ribbon next to Swiss Federal Railways (SBB) CEO Andreas Meyer during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Liechtenstein's Prime Minister Adrian Hasler addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich

Liechtenstein's Prime Minister Adrian Hasler addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Austrian Chancellor Christian Kern addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann

Austrian Chancellor Christian Kern addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

French President Francois Hollande gestures after his address during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich

German Chancellor Angela Merkel addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

German Chancellor Angela Merkel addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

French President Francois Hollande addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

French President Francois Hollande addresses the guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

French President Francois Hollande addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

German Chancellor Angela Merkel addresses the guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. REUTERS/Arnd Wiegmann 

French President Francois Hollande addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

German Chancellor Angela Merkel addresses the guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

German Chancellor Angela Merkel addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Pollegio, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich TPX IMAGES OF THE DAY

(L-R) German Chancellor Angela Merkel, Swiss Interior Minister Alain Berset and French President Francois Hollande arrive in Pollegio for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

(L-R) Italian Prime Minister Matteo Renzi, Austrian Chancellor Christian Kern and French President Francois Hollande arrive in Pollegio for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, Switzerland June 1, 2016. REUTERS/Ruben Sprich 

(L-R) French President Francois Hollande, German Chancellor Angela Merkel and Swiss Federal President Johann Schneider-Ammann arrive in Pollegio for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

(L-R) French President Francois Hollande, German Chancellor Angela Merkel and Swiss Federal President Johann Schneider-Ammann arrive in Pollegio for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

(L-R) Italian Prime Minister Matteo Renzi, Swiss Federal President Johann Schneider-Ammann, French President Francois Hollande and German Chancellor Angela Merckel travel in the VIP train, during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Gotthard, Switzerland June 1, 2016. REUTERS/Ruben Sprich TPX IMAGES OF THE DAY

(L-R) Italian Prime Minister Matteo Renzi, Swiss Federal President Johann Schneider-Ammann, French President Francois Hollande and German Chancellor Angela Merckel travel in the VIP train, during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, in Gotthard, Switzerland June 1, 2016. REUTERS/Ruben Sprich 

Guests look at screens during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Guests look at screens during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Swiss President Johann Schneider-Ammann (R) welcomes French President Francois Hollande for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. REUTERS/Ruben Sprich 

Performers dressed as miners, take part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich

Swiss President Johann Schneider-Ammann (R) welcomes German Chancellor Angela Merkel for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann (R) welcomes German Chancellor Angela Merkel for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann (R) welcomes Italian Prime Minister Matteo Renzi for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann (R) welcomes Italian Prime Minister Matteo Renzi for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. REUTERS/Ruben Sprich 

Guests waves at a train that has crossed the tunnel during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

A stagecoach pulled by horses takes part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Performers dressed as miners, take part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann

Performers dressed as miners, take part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann (SWITZERLAND - Tags: POLITICS TRANSPORT ENTERTAINMENT)

Performers dressed as miners, take part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

A performer dressed as a bird takes part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Performers dressed as miners, take part in a show during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann addresses guests while Swiss Transport Minister Doris Leuthard appears on a screen during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. REUTERS/Arnd Wiegmann 

Guests use their mobile devices during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016.The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Former Swiss transport minister Adolf Ogi (R) talks with former German foreign minister Joschka Fischer before the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. REUTERS/Arnd Wiegmann 

Swiss President Johann Schneider-Ammann (R) welcomes Austrian Chancellor Christian Kern for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann (R) welcomes Liechtenstein's Prime Minister Adrian Hasler for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss Foreign Minister Didier Burkhalter (R) welcomes Liechtenstein's Prime Minister Adrian Hasler with Swiss President Johann Schneider-Ammann (C) for the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Ruben Sprich 

Swiss President Johann Schneider-Ammann addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Swiss President Johann Schneider-Ammann addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann 

Swiss President Johann Schneider-Ammann addresses guests during the opening ceremony of the NEAT Gotthard Base Tunnel, the world's longest and deepest rail tunnel, near the town of Erstfeld, Switzerland June 1, 2016. The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc (23.1 billion USD) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, that divides Europe's north and south. REUTERS/Arnd Wiegmann