Around 1300 the Jena city fortifications had progressed so far that one could speak of a closed complex. It consisted of moats, walls, kennel areas, 3 gate towers, 4 corner bastions and 12 shell towers that were added later. The powder tower at the northwest corner of the city wall is about 20 m high and has 4 floors with a gallery. Together with the reconstructed battlement, the house on the wall and the Johannistor, this is the largest surviving part of the former Jena city fortifications.
The tower has only one entrance, a low gate about 7 m high. This gate can be reached via the reconstructed battlements. The old trade route from Erfurt to Altenburg led through the nearby Johannistor. One of four suburbs of medieval Jena, the Johannisvorstadt, lay in front of the ensemble (Wikipedia).