Berlin U-Bahn U7

U7 is Berlin's longest U-Bahn line, 31.8 km and 40 stations, running entirely underground from Rudow in the southeast to Rathaus Spandau in the northwest. It was built out in the postwar decades, south to Rudow between 1963 and 1972 and west to Spandau between 1966 and 1984, and its stations carry the bold colored tilework of Rainer Rummler's 1970s West Berlin designs.

There is no station at BER. The airport connects to U7 only by the X7 express bus to Rudow, which works if you are staying along the line in Neukolln, though the FEX and S-Bahn are the direct routes to the center. Most stations have elevators after the BVG retrofit, but confirm your stop if you need level access.