Ruislip depot is a traction maintenance depot on the London Underground Central line, between the stations of Ruislip Gardens and West Ruislip in the London Borough of Hillingdon. During the Second World War, anti-aircraft guns were made at Ruislip Depot. Part of the depot was retrofitted with a green roof, as a trial for a larger-scale rollout across London Underground. The scheme was monitored by the University of East London.