above-listed stations, multiple stations in the Berlin area that were of high importance during the Cold War rapidly lost importance and passengers after reunification, some to the point of becoming ghost stations. The most notable examples are: : station on the Berlin Outer Ring located due south of Berlin, quite far from any populated place, lost its importance with the resumption of direct routes from the Potsdam area to East Berlin and due to the reduction of the workforce in the factory located nearby. Trains running between Potsdam and the station stopped at the station until December 2012. Since then all passenger trains pass through without stopping and it was officially reclassified to a (service station). A train stop named was built 2 km to the west (closer to populated areas) and brought into service with the closure of the station. : an interchange station also located on the Berlin Outer Ring on the outskirts of Potsdam, named (Potsdam Main station) between 1961 and 1993, was the most important station of Potsdam when the traffic flow to West Berlin (Berlin–Magdeburg railway) was severely restricted. After resumption of service between Potsdam and station, the station lost its importance, became unstaffed in 1994. Tracks on the upper deck were demolished in 1999 (leaving only a pair of through tracks not adjacent to any platform), and on the lower deck only a single platform was left in service for use by the local trains from Potsdam to . Although its present-day importance is negligible and its decaying appearance is not unlike "real" ghost stations from the Cold War era, it still has regular passenger trains stopping at it. Due to the delays in opening Berlin Brandenburg Airport the train station serving it (which was ready for use on the originally planned opening date in 2012) was served by empty trains to prevent mold. Französische Straße (Berlin U-Bahn) mentioned above shut down permanently in December 2020 when the new interchange station with the extended U5 opened as the two are too close to each other. It is thus the only Berlin U-Bahn station to be a ghost station twice over and for entirely different reasons. Ghost stations elsewhere Argentina The Underground has four ghost stations. The two stations on Line A were originally two single-platform stations closed in 1953 since their close proximity meant trains had to stop in quick succession and frequencies were