Fireworks explode over Brandenburg Gate in Berlin on Monday as part of the celebrations marking the 20th anniversary of the fall of the Berlin Wall. Wolfgang Rattay/AFP/Getty Images hide caption

itoggle caption Wolfgang Rattay/AFP/Getty Images

Checkpoint Charlie shown in June 1968 (left) and October 2009 (right). During the Cold War, Checkpoint Charlie was the main border crossing between East and West Berlin; today, the historic site is a popular shopping district and tourist attraction. John MacDougall/AFP/Getty Images hide caption

itoggle caption John MacDougall/AFP/Getty Images