Hackney Marshes is an area of open space in London's Lower Lea Valley, lying on the western bank of the River Lea. It takes its name from its position on the eastern boundary of Hackney, the principal part of the London Borough of Hackney, and from its origin as an area of true marsh. The marshes were extensively drained from Medieval times onwards, and rubble was dumped here from buildings damaged by air raids during World War II, raising the level of the ground.