The outer ditch of the place, also the town ditch, commenced in a deep ravine close north of the keep, and was carried along the north front, skirting what are called “the Flats”; thence along the east front, between the wall and the town, and thence round the south end, and so beneath a part of the west front, until it is lost in the steep ground near the bridge, having been altogether nearly 700 yards in length.