Here's a geographic fact that surprises many: Berlin has no towns or cities within it. As one of Germany's three city-states (Stadtstaaten), alongside Hamburg and Bremen, Berlin is both a city and a federal state—administratively indivisible.
Unlike Munich (in Bavaria) or Cologne (in North Rhine-Westphalia), which are municipalities within larger states, Berlin's boundaries are the state boundaries. Its twelve boroughs (Bezirke)—Mitte, Friedrichshain-Kreuzberg, Pankow, etc.—are administrative districts, not independent municipalities. They have local councils and mayors, but no separate legal personality.
This unique status dates to 1920's Greater Berlin Act, which consolidated eight towns, fifty-nine rural communities, and twenty-seven estate districts into a single municipal entity. Post-war division and reunification preserved the structure.
So when someone asks for "cities in Berlin," the answer is simple: there's only one. Berlin itself. Everything else is a neighborhood, a district, or a Kiez—the hyperlocal quarters that give the city its textured, village-like character within a metropolis of 3.8 million.