Alte Burg, Medieval castle ruins in Rothenburg ob der Tauber, Germany

Alte Burg is a medieval fortress sitting on a ridge above the Tauber Valley with remnants of circular defensive walls, gates, and the Blasius Chapel still standing. The surviving structures form part of Rothenburg's historic layout, with some walls now incorporated into modern buildings.

Around 1142 King Conrad III built a new royal castle on the spur above the Tauber, exchanging the site from the Neumünster foundation; the original charter of Bishop Embricho of Würzburg survives. In 1188 the castrum Rotenburch appears in a treaty between Frederick Barbarossa and Alfonso VIII of Castile. In 1407 the town council had the castle slighted, and King Wenceslaus granted them the eastern bergfried and adjoining walls, a donation confirmed by Sigismund in 1425.

The Blasius Chapel remains visible in the ruins today with its mix of Romanesque and Gothic architectural details. This small sanctuary reflects the religious life that once centered on the fortress grounds.

The castle site lies on the wooded spur west of the old town, reached on foot from the Burggarten; the Blasius Chapel there is freely accessible. The ring wall, the Romanesque gate now serving as the base of the Gärtnerhaus, and the chapel's Romanesque palas remains can be picked out along the circuit. The gate was first examined archaeologically in 2007.

Local residents salvaged stones from the demolished fortress to build and repair their own houses after 1407. This is why sections of the original medieval walls now form the foundations and outer walls of private homes throughout the old town.