BER isn't really an expansion, it is replacing the two other airports in Berlin that were more central and had to close down (because they were old and too cent

BER isn't really an expansion, it is replacing the two other airports in Berlin that were more central and had to close down (because they were old and too central to not be a major noise problem), Tegel (TXL) and Tempelhof (THF) and parts of the old function of Schoenefeld (SXF, formerly a regular airport, now just a government airfield, but right next to/part of BER).