The Oberbaum Bridge (German: Oberbaumbrücke) is a double-deck bridge crossing Berlin's River Spree, considered one of the city's landmarks. It links Friedrichshain and Kreuzberg, former boroughs that were divided by the Berlin Wall, and has become an important symbol of Berlin's unity. The bridge is built on the former boundary of the municipal area with its rural environs, where an excise wall was built in 1732. A wooden drawbridge was built as part of the wall; it served as a gate to the city. The name Oberbaumbrücke stemmed from the heavy tree trunk, covered in metal spikes, that was used as a boom to block the river at night to prevent smuggling. (Baum means tree or wooden beam in German; thus the name means something like "Upper [Upstream] Tree Bridge"; there was another tree-trunk barrier at the western end of the contemporary city limits). By 1879, the bridge had grown but needed to be redone. The Siemens & Halske company, which was planning to build the Berlin U-Bahn (subway), insisted on a combined crossing for road vehicles, pedestrians, and the new rail line. The architect and government official Otto Stahn (1859-1930) designed it in the North German Brick Gothic style of a city gate. The new bridge opened in 1896 after two years of construction. When the Berlin Wall was built in 1961 the bridge became part of East Berlin's border with West Berlin, and became a pedestrian crossing for West Berlin residents. (wikipedia.org)