This typical medieval castle, built at the end of the 12C, has a trapezoidal plan, with three round towers and a rectangular dungeon (the fourth tower, with machicolations, was added in the 14C). Granted to Marshal Vauban in 1675 as a reward for taking Maastricht, he converted it into a garrison. The interior has been recently restored and features extensive furnishings, enabling visitors to find out more about this brilliant engineer (who was also an enlightened writer).