This old and massive brick fortress (13C) stands beside the IJmeer and the mouth of the Vecht. It has heavy angle towers and is surrounded by ditches. From 1621, the castle was the location for an intellectual and literary circle formed around P.C. Hooft (historian, poet and owner), the Muiderkring, which hosted celebrities such as Vondel and C. Huygens. The castle has furniture, paintings, weapons and armour from the 17C.