The outer bailey of Kenilworth Castle is usually entered through Mortimer's Tower, today a modest ruin but originally a Norman stone gatehouse, extended in the late 13th and 16th centuries.[1] The outer bailey wall, long and relatively low, was built mainly by King John; it has numerous buttresses but only a few towers, being designed to be defended primarily by the water system of the Great Mere and Lower Pool.[5] The north side of the outer bailey wall was almost entirely destroyed during the slighting.[5] Moving clockwise around the outer bailey from Mortimer's Tower, the defences include a west-facing watergate, which would originally have led onto the Great Mere; the King's gate, a late 17th-century agricultural addition; the Swan Tower, a late 13th-century tower with 16th-century additions, then named after the swans that lived on the Great Mere; the early 13th-century Lunn's Tower; and the 14th-century Water Tower, so named because it overlooked the Lower Pool.[8]