In shaping a coherent urban center since the fall of the Wall in 1989, the city of Berlin has faced immense challenges: the lingering destruction from the Second World War and the brutal 30-year urban bifurcation, and then the integration of the sprawling federal bureaucracy, once the city became the capital again, of a reunited Germany. The Planwerk Innenstadt (City Center Plan Guide), from 1999, called for such strategies as a uniform building height of 72 feet, limited dimensions of window openings, and maintaining the existing pattern of city blocks to create viable urban spaces and a sense of historical continuity. Revisions made in 2010 proposed specific interventions, like the reconstruction of key monuments and public spaces for 11 areas in the former East and West. Although there are some exceptions, such as the high-rises clustered around Potsdamer Platz and the Zoo train station, as well as those planned for the Alexanderplatz, an embrace of historical models, as inspiration for the new and as a basis for direct imitation in rebuilding, is at the heart of these measures.