Kasteel Radboud (Radboud Castle) - also knwon as Kasteel Medemblik - is located between the harbour of Medemblik and the IJsselmeer. At the end of the 13th century, Count Floris V of Holland ordered the construction of a series of castles to control the Westfrisian population. Radboud Castle is the only one remaining of those castles. When exactly it was built is unknown, but the castle was completed before the so called St. Lucia's Flood in December 1287.

From old pictures and archeological research it is known that Radboud Castle must have been a strong castle. Nowadays only two residential wings, two square and one round tower are still standing.

In the 14th and 15th century the counts of Holland installed guardians at the castle. Radboud Castle has never been connected to nobility but has been primarily used as a prison. The people of Medemblik used it also as a refuge. The defensive function of the castle was reduced with the building of walls around the city of Medemblik at the end of the 16th century and due to both dismantling and lack of maintenance there was attrition of the castle buildings.

From 1848 the demolition of the castle buildings started. In 1889 the remains of the castle were transferred to the state and a thorough restoration followed. From 1897 till 1934 the castle was used as a courthouse. From 1964 to 1965 further restorations were done with a more historical and architectural correctness and some of the previous renovations were removed

The name Radboud has been derived from the popular assumption that the castle was built on the place where in the 8th century a castle from the Frisian king Radboud had been standing.
Nowadays Kasteel Radboud houses a museum, while on the ground flore there is a café/restaurant.