Underneath Potsdamer Platz.
Potsdamer Platz is an important public square and traffic intersection in the centre of Berlin, Germany, lying about 1 km (1,100 yd) south of the Brandenburg Gate and the Reichstag (German Parliament Building), and close to the southeast corner of the Tiergarten park. It is named after the city of Potsdam, some 25 km (16 mi) to the south west, and marks the point where the old road from Potsdam passed through the city wall of Berlin at the Potsdam Gate. After developing within the space of little over a century from an intersection of rural thoroughfares into the most bustling traffic intersection in Europe, it was totally laid waste during World War II and then left desolate during the Cold War era when the Berlin Wall bisected its former location. Since German reunification, Potsdamer Platz has been the site of major redevelopment projects.