Ouborgh Castle, locally known as Kasteel Ouborgh, Oudborg, Aldenborg or Naborch, lies west of the town of Swalmen, in the province of Limburg in the Netherlands.
The remains of Ouborgh Castle can be found west of the railway line Venlo-Roermond on the banks of the Swalm stream. Ouborgh Castle is a 14th century motte castle. It has an octagonal keep which is unique for the Netherlands.
This partly remaining octagonal keep was originally part of a bigger castle which was built in the first half of the 14th century, probably built by a Seger Vosken van Swalmen.
In 1381 the castle was sold by Robijn van Swalmen to his nephew Dirk van Oost. Dirk however also built the nearby Hillenraad Castle and Ouborgh Castle probably fell into disuse.
The ground plan of this castle was a moated and walled rectangle. Against the outer wall of this rectangle two wings were built at right angles with each other. The octagonal keep was situated at the southwestern corner of the rectangle. Inside the keep you can see the springing lines of a vaulted cellar and traces of a spiral staircase next to the small entrance in its north eastern wall.
Around 1450 the castle already seems to have been uninhabited, probably because of a fire. And in 1660 it had decayed to become a picturesque ruin. There is very little known about it's history. So if someone knows anything more about it, please let me know.
In 1916 the castle ruins were used as a quarry for 'authentic' building materials for the restoration of the church in the nearby village of Asselt. In 1962 archeological excavations were carried out.
The ruins are in bad shape and seem to be crumbling away due to overgrown vegetation and frost. It is freely accessible.