This characteristic medieval castle, built in the late 12C, sports a trapezoidal plan, with three round towers and a rectangular keep (the fourth tower, with machicolations, was added in the 14C). Marshal Vauban was given the property in 1675 as thanks for taking Maastricht; he converted it into a garrison. The interior has recently been restored and entirely refurnished, enabling visitors to find out more about this brilliant engineer and enlightened writer.