Burg Altraderach, Medieval castle ruins near Kluftern, Friedrichshafen, Germany

Burg Altraderach is a castle site near Kluftern in Friedrichshafen, visible today as a fortified enclosure with earthwork defenses. A circular ditch with an embankment marks the perimeter, with steep slopes falling away to the east and a high embankment rising to the north.

The castle was built in the 12th century by the Lords of Raderach and first mentioned in 1160, when Werner of Raderach witnessed the transfer of serfs to St. Blaise Abbey. On 14 March 1280, Count Manegold of Nellenburg promised the Bishop of Constance to free the Castrum in Radray from feudal ties and transfer it as property to the Hochstift Constance. The castle was later abandoned.

Local tradition places Christoph von Schmid's tale Rosa von Tannenburg here, with the Old Castle identified as the Tannenburg. The vanished New Castle, the Fichtenburg, is also set in Raderach. Two streets recall this: Fichtenburgstraße in Raderach and Tannenburgstraße in nearby Unterraderach.

The site is reachable on foot and invites a walk through the surrounding area where the earthworks are easy to spot. Visit during dry weather if possible, as the paths can become muddy otherwise.

The northern area preserves a moat approximately 2.5 meters (8 feet) deep, interrupted at the northwestern corner. This gap reveals where the original entrance to the fortress likely stood.