Festung Heldrungen, Medieval fortress in Heldrungen, Germany

Festung Heldrungen is a fortress in Heldrungen, Thuringia, with a Renaissance castle core built from 1512 to 1518 for Count Ernst II of Mansfeld. The castle has three of its original four wings, a Romanesque bergfried called the Müntzer Tower, and Gothic window arrangements. The outer defences, added from 1664 to 1668 by Johann Moritz Richter, follow Vauban's system with four bastions and two moats.

The fortress developed during the medieval period into an important defensive installation for local rulers. In 1525, it served as a prison during the German Peasants' War, notably holding Thomas Müntzer before his execution.

The name Müntzer Tower recalls Thomas Müntzer, held here after the Battle of Frankenhausen on 15 May 1525 before being handed to the Mühlhausen authorities for execution. Since 1976 a monument by Hans-Hermann Richter and Johann-Peter Hinz stands on the open square before the north wing, showing the captive reformer framed by princely mercenaries, with a young couple and three beaten peasants.

The outer grounds are freely accessible, while guided tours through bastions and interior rooms are arranged by the local heritage association. Visitors should check opening times and tour schedules in advance to plan their visit effectively.

A tunnel system connects the inner and outer moats beneath the bastion wall, an unusual feature in German fortress design. This underground passage historically enabled quick defensive movements between fortification levels.