Heathrow serves the largest International airport and the busiest transport hub in the UK and lies in the London Borough of Hillingdon. To the north, the airport is surrounded by the built-up areas of Harlington, Harmondsworth, Longford and Cranford. To the east are Hounslow and Hatton, and to the south are East Bedfont and Stanwell. To the west, the M25 motorway separates the airport from Colnbrook in Berkshire.