Hamburg
Hamburg got its first U-Bahn line in 1912, when the section from Rathaus to Barmbek opened as the start of today's U3 ring, though electric suburban trains had been running since 1907. Despite the U for underground, much of the network runs above ground, and the U3 includes an elevated stretch along the harbor. In the century since, the network has kept growing. The S-Bahn reached Hamburg Airport in 2008, and the U4, opened in 2012, runs into the new HafenCity district and was extended to Elbbrucken in 2018.
