Historical version 7 of Heathrow Terminals 1, 2, And 3 Station (view current version)

Zone 6 Tube station on the Piccadilly Line. All Piccadilly Line services call at this station.

Actually inside Heathrow Airport. Close to the Heathrow Central Bus Station, and the Heathrow Connect and Heathrow Express services also call here. According to Wikipedia, passengers transferring between Terminals 1/2/3 and Terminal 4 can use the Heathrow Connect service free of charge, and those transferring between Terminals 1/2/3 and Terminal 5 can use the Heathrow Express service free of charge.

See also:

OS X co-ord: 507549 OS Y co-ord: 175844 (Latitude: 51.470840 Longitude: -0.451384)
This is version 7 (as of 2008-05-10 11:12:31). View current version. List all versions.