Ruislip Lido was initially created as a reservoir, for the Grand Junction Canal in 1811, it is still a reservoir, but with the addition of an artificial beach. The lido is located in Ruislip, within the London Borough of Hillingdon, England, situated between Ruislip Common, Ruislip Woods (a Site of Special Scientific Interest), and Poors Field.
Originally opened as a feeder reservoir for the Grand Junction Canal in 1811, the reservoir was reopened in 1933 as a lido, with facilities for swimming and boating. A narrow gauge railway, the Ruislip Lido Railway was opened in 1945, and now runs about two-thirds of the distance around the reservoir.
During the 1970s and 1980s, the Lido had fallen into a state of disrepair, the lido has since undergone renewal works and was the subject of an enhancement project unveiled by the London Borough of Hillingdon in January 2010. The project involved the return of boating and swimming in the reservoir, which had previously not been possible due to pollution and an artificially low water level.