A moat is found surrounding the castle and its donjon. The donjon had movable gates which separated the palace from the castle. The donjon of Matsumoto Castle is one of Japan's oldest existing five stories Tenshu. The castle is an Anglo-Norman donjon (keep). Douglas commenced rebuilding Bothwell, repairing the donjon and completing the walls. This fortification was quickly expanded with water works and a donjon (castle keep). A donjon or keep is a defensive tower. A third innovation of the Azuchi Castle was the high central tower, or "donjon". The inner courtyard was overrun and the garrison retreated to the donjon or keep. "Dungeon" is a corrupted form of "donjon" and means a dark, unwelcoming prison. Bishop Guillaume fortified the cathedral's precincts and provided it with a 35-metre "donjon" (keep). He did not marry and apparently lived in the Donjon tower. Only twelve castles have a "donjon" that is considered original. The structures listed include "donjon", watch towers and connecting galleries. In 1585 the Inner donjon was completed.