Besides the water board facilities and the New River, Clissold Park contains two large ornamental lakes, a home to many water birds and a population of terrapins. These lakes—purportedly the remains of clay pits dug for the bricks used in the building of Clissold House—are all that is left to mark the course of the Hackney Brook, one of London's lost rivers, which once flowed from west to east across Stoke Newington on its way to the River Lea. In flood at this point, the brook was known to span 10 metres. The two lakes are not fed from the brook, which has disappeared into the maze of sewers under London, but from the mains supply—the New River.