Berlin is currently one of the most exciting cities in the world. Evidence of its tumultuous history is everywhere. The Sputnik-inspired Fernsehturm (Television Tower) stands directly behind the Gothic St. Mary’s Church, whose stubborn angle in an otherwise rectilinear square is a reminder of the medieval streets cleared to make way for an expanded Alexanderplatz, the communist showplace of East Berlin. Just across the river, bullet holes from World War II pock the neoclassical colonnade of the Alte Nationalgalerie. Improbably, the Stadtschloss — the seat of the Prussian kings demolished in 1950 — is being rebuilt nearby. And in bustling Potsdamer Platz, the soaring Sony Center incorporates the ornate wall of a prewar ballroom into its otherwise contemporary façade. Sections of a much more infamous wall stand a few feet away.