A woman stands next to three stalactites in a long natural ice cave created by melted water accumulated during the summer and by a siphon effect leaves in the autumn giving way to an ice cathedral, at the Glacier 3000 ski resort in Les Diablerets, Switzerland, December 22, 2021. REUTERS/Denis Balibouse 

A stalactite is pictured in a 15m long natural ice cave created by melted water accumulated during the summer and by a siphon effect leaves in the autumn giving way to an ice cathedral, at the Glacier 3000 ski resort in Les Diablerets, Switzerland, December 22, 2021. REUTERS/Denis Balibouse 

Icicles hang on a bog where 12,000 years ago was the Schaufelferner glacier at 2,280 meters above sea level, at Stubaier glacier ski resort near Neustift im Stubaital, Austria, October 22, 2018. REUTERS/Lisi Niesner SEARCH "AUSTRIA GLACIERS" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A salt stalactite is seen inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

A salt stalactite is seen inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

Salt stalactites are seen inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

Efraim Cohen, a member of Hebrew University's Cave Research Center, stands next to salt stalactites inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

Salt stalactites are seen inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

Boaz Langford, a member of Hebrew UniversityÕs Cave Research Center and head of the 2019 Malham Cave Mapping stands next to salt stalactites inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

Salt stalactites are seen inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

Salt stalactites are seen inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

A woman looks at salt stalactites inside the Malham Cave, which Israeli researchers say is the world's longest salt cave, in Mount Sodom near the Dead Sea, Israel March 27, 2019. Picture taken March 27, 2019. REUTERS/Nir Elias 

A duck looks at icicles at a pond in Bern, Switzerland February 26, 2018. REUTERS/Stefan Wermuth TPX IMAGES OF THE DAY 

A lone visitor takes a picture near the brink of the ice covered Horseshoe Falls in Niagara Falls, Ontario, Canada, January 3, 2018. REUTERS/Aaron Lynett 

A tourist looks at the stalactites and stalagmites inside the 'Quiocta' cavern in Chachapoyas, Peru, November 15, 2017. Picture taken November 15, 2017. REUTERS/Guadalupe Pardo 

Stalactites and stalagmites are seen at the 'Quiocta' cavern in Chachapoyas, Peru, November 15, 2017. Picture taken November 15, 2017. REUTERS/Guadalupe Pardo 

Stalactites are seen at the 'Quiocta' cavern in Chachapoyas, Peru, November 15, 2017. Picture taken November 15, 2017. REUTERS/Guadalupe Pardo 

A water drop hangs on a stalactite along the bank of the River Thames during low tide in London, Britain February 24, 2017. REUTERS/Stefan Wermuth SEARCH "THAMES WERMUTH" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

Stalactites are seen along the bank of the River Thames during low tide in London, Britain February 24, 2017. REUTERS/Stefan Wermuth SEARCH "THAMES WERMUTH" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

People tour the Luray Caverns in Luray, Virginia, July 30, 2015. The caverns, some as deep as 164 feet below the earth, featuring stalactites, stalagmites, are a top tourist attraction and see thousands of visitors each year. Photo taken July 30, 2015 REUTERS/Carlo Allegri 

A general view of the Fairy Grottoes (Feengrotten) in the eastern German town of Saalfeld, March 19, 2014. Discovered in 1913 inside a former slate mine, the colourful caves are full of stalactites and stalagmites. REUTERS/Fabrizio Bensch (GERMANY - Tags: SOCIETY) 

Visitors tour the Fairy Grottoes (Feengrotten) in the eastern German town of Saalfeld, March 19, 2014. Discovered in 1913 inside a former slate mine, the colourful caves are full of stalactites and stalagmites. REUTERS/Fabrizio Bensch (GERMANY - Tags: SOCIETY) 

A visitor walks in the Chamber of Stalactites and Stalagmites at the Nemocon salt mine September 26, 2012. The mine is one of Colombia's most popular tourist attractions. World Tourism Day falls on September 27. REUTERS/Jose Miguel Gomez (COLOMBIA - Tags: SOCIETY ENVIRONMENT TRAVEL) 

Visitors look at the Chamber of Stalactites and Stalagmites in the Nemocon salt mine September 26, 2012. The mine is one of Colombia's most popular tourist attractions. World Tourism Day falls on September 27. REUTERS/Jose Miguel Gomez (COLOMBIA - Tags: SOCIETY ENVIRONMENT TRAVEL) 

Visitors walk past lanterns in the underground cave portion of the Underground Fluorescent park in Yishui November 4, 2011. A Chinese tourism company listed in the United States wants investors to pour their money down a dark hole. The attraction, about an hour's drive outside the smoggy city of Linyi in the eastern province of Shandong, promises visitors 3 km (2 miles) of grand stalactites, multicolored lights and an exciting luge ride. To match Feature CHINA CAVE/ REUTERS/Melanie Lee (CHINA - Tags: TRAVEL BUSINESS POLITICS) 

Visitors walk towards the entrance of the Underground Fluorescent Lake attraction in Yishui November 4, 2011. A Chinese tourism company listed in the United States wants investors to pour their money down a dark hole. The attraction, about an hour's drive outside the smoggy city of Linyi in the eastern province of Shandong, promises visitors 3 km (2 miles) of grand stalactites, multicolored lights and an exciting luge ride. To match Feature CHINA CAVE/ REUTERS/Melanie Lee (CHINA - Tags: TRAVEL BUSINESS POLITICS) 

Employees man ticket turnstiles at the Underground Fluorescent Lake attraction in Yishui November 4, 2011. A Chinese tourism company listed in the United States wants investors to pour their money down a dark hole. The attraction, about an hour's drive outside the smoggy city of Linyi in the eastern province of Shandong, promises visitors 3 km (2 miles) of grand stalactites, multicolored lights and an exciting luge ride. Tracing the attraction's ticket receipts back to investors in the United States proves an even more complex labyrinth to navigate. To match Feature CHINA CAVE/ REUTERS/Melanie Lee (CHINA - Tags: TRAVEL BUSINESS POLITICS) 

A general view of the lower cave of Jeita Grotto in Jeita, north of Beirut October 4, 2011. In an attempt to boost tourism, Lebanon has been campaigning to have the Jeita Grotto chosen as one of the "Seven Wonders of Nature" in an international competition.The cave system, which is home to the longest stalactite on the planet at over 8 m (26 feet), was entered into the '"New Seven Wonders of Nature" contest in 2007 and Lebanon is trying to shore up votes in the global poll which ends next month. Picture taken October 4, 2011. To match Feature LEBANON-TOURISM/ REUTERS/ Sharif Karim (LEBANON - Tags: ENVIRONMENT TRAVEL) 

Tourists view the lower cave of the Jeita Grotto by boat in Jeita, north of Beirut, October 4, 2011. In an attempt to boost tourism, Lebanon has been campaigning to have the Jeita Grotto chosen as one of the "Seven Wonders of Nature" in an international competition.The cave system, which is home to the longest stalactite on the planet at over 8 m (26 feet), was entered into the '"New Seven Wonders of Nature" contest in 2007 and Lebanon is trying to shore up votes in the global poll which ends next month. Picture taken October 4, 2011. To match Feature LEBANON-TOURISM/ REUTERS/ Sharif Karim (LEBANON - Tags: ENVIRONMENT TRAVEL) 

A tourist views the Jeita Grotto in Jeita, north of Beirut, October 4, 2011. In an attempt to boost tourism, Lebanon has been campaigning to have the Jeita Grotto chosen as one of the "Seven Wonders of Nature" in an international competition.The cave system, which is home to the longest stalactite on the planet at over 8 m (26 feet), was entered into the '"New Seven Wonders of Nature" contest in 2007 and Lebanon is trying to shore up votes in the global poll which ends next month. Picture taken October 4, 2011. To match Feature LEBANON-TOURISM/ REUTERS/ Sharif Karim (LEBANON - Tags: ENVIRONMENT TRAVEL) 

Tourists view the Jeita Grotto in Jeita, north of Beirut, October 4, 2011. In an attempt to boost tourism, Lebanon has been campaigning to have the Jeita Grotto chosen as one of the "Seven Wonders of Nature" in an international competition.The cave system, which is home to the longest stalactite on the planet at over 8 m (26 feet), was entered into the '"New Seven Wonders of Nature" contest in 2007 and Lebanon is trying to shore up votes in the global poll which ends next month. Picture taken October 4, 2011. To match Feature LEBANON-TOURISM/ REUTERS/ Sharif Karim (LEBANON - Tags: ENVIRONMENT TRAVEL) 

Stalactites hanging from the Jeita Grotto ceiling is seen during a media day tour to campaign for the selection of the Jeitta Grotto as one of the seven natural wonders of the world July 1, 2008. The Jeita Grotto is a compound of karstic limestone caves in Lebanon located 20 kilometres north of Beirut in the Valley of Nahr al-Kalb (Dog River). The grotto complex is made up of two caves, upper galleries and a lower cave through which an underground river runs. Picture taken July 1, 2008. REUTERS/Mohamed Azakir (LEBANON) 

A general view of stalactites and stalagmites in the Jeita Grotto during a media day tour to campaign for the selection of the Jeitta Grotto as one of the seven natural wonders of the world July 1, 2008. The Jeita Grotto is a compound of karstic limestone caves in Lebanon located 20 kilometres north of Beirut in the Valley of Nahr al-Kalb (Dog River). The grotto complex is made up of two caves, upper galleries and a lower cave through which an underground river runs. REUTERS/Mohamed Azakir (LEBANON) 

Stalactites are seen in the Jeita Grotto during a media day tour to campaign for the selection of the Jeitta Grotto as one of the seven natural wonders of the world July 1, 2008. The Jeita Grotto is a compound of karstic limestone caves in Lebanon located 20 kilometres north of Beirut in the Valley of Nahr al-Kalb (Dog River). The grotto complex is made up of two caves, upper galleries and a lower cave through which an underground river runs. REUTERS/Mohamed Azakir (LEBANON) 

A general view of stalactites and stalagmites in the Jeita Grotto during a media day tour to campaign for the selection of the Jeitta Grotto as one of the seven natural wonders of the world July 1, 2008. The Jeita Grotto is a compound of karstic limestone caves in Lebanon located 20 kilometres north of Beirut in the Valley of Nahr al-Kalb (Dog River). The grotto complex is made up of two caves, upper galleries and a lower cave through which an underground river runs. REUTERS/Mohamed Azakir (LEBANON) 

A close up of stalactites hanging from the Jeita Grotto ceiling is seen during a media day tour to campaign for the selection of the Jeitta Grotto as one of the seven natural wonders of the world July 1, 2008. The Jeita Grotto is a compound of karstic limestone caves in Lebanon located 20 kilometres north of Beirut in the Valley of Nahr al-Kalb (Dog River). The grotto complex is made up of two caves, upper galleries and a lower cave through which an underground river runs. Picture taken July 1, 2008. REUTERS/Mohamed Azakir (LEBANON) 

A man walks during his visit to the Grotto of Marvels in Aracena, southwest Spain December 8, 2006. The Grotto of Marvels, lined with stalactites and stalagmites, is the most extensive cavern of the Iberian peninsula of calcareous formation. REUTERS/Marcelo del Pozo (SPAIN) 

People walk during their visit to the Grotto of Marvels in Aracena, southwest Spain December 8, 2006. The Grotto of Marvels, lined with stalactites and stalagmites, is the most extensive cavern of the Iberian peninsula of calcareous formation. REUTERS/Marcelo del Pozo (SPAIN) 

People walk during their visit to the Grotto of Marvels in Aracena, southwest Spain December 8, 2006. The Grotto of Marvels, lined with stalactites and stalagmites, is the most extensive cavern of the Iberian peninsula of calcareous formation. REUTERS/Marcelo del Pozo (SPAIN) 

People walk during their visit to the Grotto of Marvels in Aracena, southwest Spain December 8, 2006. The Grotto of Marvels is lined with stalactites and stalagmites and is the most extensive cavern of the Iberian peninsula of calcareous formation. REUTERS/Marcelo del Pozo (SPAIN) 

People walk during their visit to the Grotto of Marvels in Aracena, southwest Spain December 8, 2006. The Grotto of Marvels is the most extensive cavern of the Iberian peninsula of calcareous formation and is lined with stalactites and stalagmites. REUTERS/Marcelo del Pozo (SPAIN)