Longstone is a suburb of Edinburgh in Scotland. It borders Saughton, Wester Hailes, Slateford, Kingsknowe and Parkhead.Longstone's most dramatic features are the Slateford Aqueduct (1822) carrying the Union Canal and the adjacent railway viaduct (1842). Underneath these runs the Water of Leith, and the canal may sometimes be seen pouring out through an overflow down into the river.