Radboud Castle (Dutch: Kasteel Radboud) is a castle on the east bank of the harbour in Medemblik. Radboud Castle is one of a number of castles in North Holland, the building was commissioned by Floris V. The exact date of building is not known but the castle was completed before the St. Lucia's Flood of 13 December 1287. On 24 June 1517 the castle saved some of the Medemblik townsfolk from the raids of Grutte Pier and his Arumer Zwarte Hoop (band of marauding pirates). On 12 August 1588 the castle surrendered to Diederik Sonoy and the Geuzen.