The Gate can be visited
Town Fortification Rostock-Stein Gate

In Rostock, the Steintor is a structure of the city fortifications, shaping the cityscape in the south of the old town. It is one of the four main gates of the former defensive complex.
History+
The first construction of the Steintor took place in 1279, shortly after the three original city centers of Rostock united in 1265 and a city fortification with walls, towers, and gates was built. It replaced the Kuhtor, located further east, as the city gate and led directly to the Neuer Markt. In 1565, conflicts arose between Rostock and Schwerin, which in 1566 led Duke Johann Albrecht I to have the Steintor, as well as parts of the city wall and other fortifications, demolished to build a fortress from the stones.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: https://commons.wikimedia.org/wiki/File:Rostock_Steintor_1.jpg
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: 54.0866, 12.1409