(Not to be confused with Hackney Marshes, Devon.) Hackney Marshes is an area of grassland on the western bank of the River Lea in the London Borough of Hackney. It was incorporated into the Lee Valley Park in 1967. It was originally a true marsh, but was extensively drained from Medieval times, and rubble was dumped here from buildings damaged by air raids during World War II. Hackney Marsh is one of the largest areas of common land in Greater London, with 136.01 hectares (336.1 acres) of protected commons.