The second opportunity i took on the Open Memorial Day was a visit of the Underground Museum¹. The Underground museum has been housed in the former signal box of the Olympic Stadium Station since 1997, hence the name “Olympic signal box”. The heart of the museum is the 14-meter-long lever mechanism of the electromechanical signal box of the VES 1913 type². VES stands for “Vereinigte Eisenbahnsignalwerke”. Commissioned in 1931 as the largest signal box of this type in Europe, the entire operation of the Betriebswerkstatt Grunewald and the Olympia-Stadion station was monitored from here. 103 points and 99 signals were set with the levers and enabled train movements with over 616 travel options. Each lever in the interlocking system controlled either a track switch (“Weiche”) or a signal, and the mechanical interlocking ensured that conflicting train routes could not be set, greatly reducing the risk of accidents. The single-row signal box was in operation from 1931 to 1983.