Berlinische Galerie is Berlin's museum for modern art, photography, and architecture, with the collection focused on work made in and around the city. It is a good counterweight to Museum Island: more 20th-century, more urban, and much more tied to Berlin's own restless cultural history.
The museum works especially well for visitors interested in Expressionism, Dada, postwar art, and the visual culture of divided Berlin. Its Kreuzberg location also makes it easy to combine with a walk toward the Jewish Museum or the old newspaper quarter.