Mündener Rotunde

The Münden Rotunda was built at the Upper Gate, the city gate first mentioned in documents in 1318. Initially, the Upper Gate had a gate tower and a drawbridge. In 1500, Duke Erich I had the Rotunda with a diameter of 17 meters and a defensive tower built here as an external bastion with a city gate. In 1776, the city gate at the Rotunda was demolished due to the construction of a highway. The defensive tower at the Rotunda was demolished in 1847. The Rotunda was preserved and continued to be used for various purposes. In 1985 and 1986, renovation work was carried out at a cost of 880,000 DM due to the increasing destruction of the building by vegetation and roots. In 2016, plans were announced to use the Rotunda for cultural events.
Source: de.wikipedia.org/wiki/Stadtbefestigung_M%C3%BCnden

The Rotunda is a former Zwinger tower that was part of the city fortifications.
Built at the beginning of the 16th century, it served to protect the city gate.
A remnant of the battlement can still be seen.

Impressive building. Unfortunately it was not possible to view the interior, so inform beforehand.