Heathrow Terminal 4 is an airport terminal at Heathrow Airport, the main airport serving London, United Kingdom, situated to the south of the southern runway, next to the cargo terminal. It is connected to Heathrow Terminals 2 and 3 by the vehicular Heathrow Cargo Tunnel, and by rail with the Heathrow Terminal 4 tube station and Heathrow Terminal 4 railway station. Built at a cost of £200 million, Terminal 4 was opened by the Prince and Princess of Wales on 1 April 1986.