After the Second World War , the railway tracks were briefly converted to Russian broad gauge in July 1945 . The Soviet dictator , Stalin took part in the Potsdam Conference and insisted on a trip without changing trains . The line was converted back to standard gauge in September of the same year . Since the line was the most important link to the USSR , neither long-distance track was dismantled for war reparations ( unlike on other lines ) , but instead both of S-Bahn tracks were dismantled . The suburban tracks were re-laid up to 1947 so that S-Bahn trains could run to Karlshorst again
Potsdam Conference
Potsdam Conference
Berlin-Karlshorst station