Berlin Ostkreuz (German for "East Crossing") is a station on the Berlin S-Bahn suburban railway and the busiest interchange station in Berlin. It is in the former East Berlin district of Friedrichshain, now part of the borough of Friedrichshain-Kreuzberg. A smaller part of the station is in Rummelsburg, part of the borough of Lichtenberg. The station is a Turmbahnhof (“tower station”, that is a two-level interchange) with the Berlin–Frankfurt (Oder) railway (“Lower Silesian–Markish Railway”) and the Prussian Eastern Railway on the lower level and the Berlin Ringbahn on the upper level.