A police marksman observes the area below from atop the Ritz Carlton Hotel at Potsdamer Platz in Berlin June 18, 2013, prior to the arrival of U.S. President Barack Obama. Obama's first presidential visit to Berlin comes nearly 50 years to the day after John F. Kennedy landed in a divided Berlin at the height of the Cold War and told encircled westerners in the city "Ich bin ein Berliner", a powerful signal that America would stand by them. REUTERS/Pawel Kopczynski (GERMANY - Tags: POLITICS CRIME LAW)