The Water Castle was the center of the manor of Millen or Milina, which was a fief of the County of Loon. She was first mentioned in 1143. The oldest known lord was Walter van Millen (Walterus de Milne), who was seneschal of Louis II van Loon. The manor was successively owned by the families de Melin, Proest (1369), van Guygoven (1456), van Berloz (1479), van Houthem (1531), de Fléron (1625) and d'Hemricourt (1741). The castle was first mentioned in 1365. The original castle was transformed into a moated castle in the 14th century. It then consisted of the older keep that was expanded into a square moated castle with a gate tower and two side towers. In the first half of the 17th century, the ruined castle was converted into a castle. It became a comfortable nobleman's home without military significance. From the 18th century onwards, the castle was no longer permanently inhabited and fell into disrepair. In 1811 it was bought by Baron de Blisia, after which much of it was demolished, including the keep and the tower on the south-west side. Only the east and west wings remained and have functioned as a farm ever since. In 1972, the remains of the castle were purchased by the municipality and restored. The 14th-century left tower made of marlstone has a Gothic vault. It is part of the east wing, the age of which may date back to the 12th century. Today the castle houses a museum, which depicts the life of the nobility in the 16th and 17th centuries. It is also the center of a number of cycling routes in the wider area that have the fortified past of the Euroregion as their theme. There is also a tourist cafe in the building and the moated castle is freely accessible.