The town of Gisoreux, the capital, sits on the River Ois. It is well fortified, with three circuits of walls which get taller and stronger as one approaches the central keep. Facing the frontier is the Duke's Keep, which watches the border to the Empire (now Marienburg) through the Grey Mountains and the Marshes of Couronne. To the east of the town are many old castles which have been left in ruins by armies attempting to invade Gisoreux.