The Fortress can be visited
Vechtach Fortress

The Vechtach Citadel is located in the city of Vechta in the federal state of Lower Saxony. Originally built in the 17th century, it once served as a defensive point and was later transformed into a cultural and recreational site.
History+
Construction of the Vechta Citadel began in 1666 under the aegis of the Münster Prince-Bishop Christoph Bernhard von Galen and was completed in 1669. The fortress, originally named “Sancta Maria,” was intended to protect the Catholic-dominated areas from the advance of Protestant forces from the direction of Bremen. In 1684, a city fire destroyed large parts of Vechta. Subsequently, the city was relocated to create a clear field of fire for the citadel, which now functioned as a standalone fortress. The original Vechta Castle was demolished, and its stones were used for the construction of the citadel's casemates. The fortress itself was designed as a regular pentagon with bastions such as St. Paulus and Christoph Bernhard, following a system by the Dutch and French fortress builders Henrick Ruse and Sébastien Le Prêtre de Vauban.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=964
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 52.7266, 8.2779