Walthamstow Marshes, Lea River, London. This raised pathway on the eastern side of the marshes follows the course of an acquaduct that once drew water from the reservoirs at Coppermill to the Middlesex Filter beds. The acquaduct has long since been filled in but you can still follow its pathway across the marshes – and if you look closely you can find remanants of old footbridges that once crossed the acquaduct…