Halle Gate
Since 1896, the electric tramway connected Treptow in the east and Berlin Zoological Garden in the west passing Belle-Alliance-Straße between Halle Gate and Yorckstraße. In 1924 and 1926, respectively, the Berlin underground opened the underground stations Belle-Alliance-Straße (Mehringdamm as of 1947) and Kreuzberg (Flughafen between 1937 and 1975; Platz der Luftbrücke since) on its north–south directed "C line" (aka Nord-Süd-Bahn; mostly today's U7).