Berlin is a city that has been broken apart and rebuilt so many times that reinvention is now its native condition. The architecture tells this directly — Schinkel's neoclassicism, Mies van der Rohe's Neue Nationalgalerie, the restored Museum Island, and the vacant lots that are still being negotiated. The city rewards those who pay attention to the surfaces.
Bauhaus discipline and postwar reinvention.
Three architectural eras are visible simultaneously: Schinkel's Prussian classicism on Museum Island, the postwar modernism of Mies van der Rohe and Hans Scharoun in the Kulturforum district, and the contested reconstruction of the GDR-era Palast der Republik site. The brutalist housing blocks of Plattenbau are their own category.
Berlin operates at its own unhurried frequency. The creative class arrived because the city asked nothing of them immediately. That quality is still present in the right neighbourhoods.
Late autumn and winter are the most considered seasons. The grey light is appropriate. Summer is too crowded and too loud for the city's natural temperament.
Mitte / Museum Island: The restored Prussian cultural core. The Pergamon, the Bode Museum, and the National Gallery occupy a river island. Allow an entire day.
Prenzlauer Berg: The neighbourhood that survived both the war and reunification with its street grid intact. Good for slow mornings and independent bookshops.
Schöneberg: Quieter than Mitte, more considered than Kreuzberg. The Bauhaus Archive is here. The Wittenbergplatz market runs on Saturday mornings.