Burg Rotwasserstelz, Medieval castle in Hohentengen am Hochrhein, Germany

Burg Rotwasserstelz is a rock castle on a 343-metre coral reef of Malm limestone in Hohentengen am Rhein, at the northern bridgehead of the Rhine crossing to Kaiserstuhl. Its present form dates from 1787. The associated buildings were the old tower, the customs office, a barn and stables, a rock cellar and the red house.

The fortress was built in the 12th century by the von Wasserstelz family and first appears in written documents from 1163. It became an important post for controlling trade routes across the High Rhine.

The castle was the seat of the Obervogt (high bailiff) of the Herrschaft Kaiserstuhl, an administrative district that included Kaiserstuhl, Lienheim, Hohentengen am Hochrhein, Herdern with the Türnerhof, Weisswasserstelz with the Guggenmühle, and Schwarzwasserstelz with Fisibach and Weiach. In 1507 Konrad IV. Heggenzer von Wasserstelz, father of Johann Melchior, held the office here. The bailiff Ludwig Tschudi von Glarus died on 23 September 1601; his epitaph is in the church of Hohentengen.

The castle remains in private ownership and can be viewed from the exterior, particularly well from paths along the riverbank. It is easily reached on foot from Hohentengen am Hochrhein and offers views across the High Rhine toward Switzerland.

The castle stands on a 343-metre coral reef of the Malm, a rock formation that also gave the castle its name Rotwasserstelz. The nearby Rhine bridge was first mentioned in 1294 and has been rebuilt many times after collapses, fires and floods.