Baumhaus Wismar

The tree house is a listed building in the Hanseatic city of Wismar, Alte Hafen, Stockholmer Straße.

The city erected the building in the first half of the 18th century in the Baroque style. At night or in the event of imminent danger, employees of the port administration, so-called Bohmschlüter, pulled a chain into the port entrance. At the same time, they also operated the turnpike for the port entrance.

de.m.wikipedia.org/wiki/Baumhaus_(Wismar)

tree house
Mid 18th century built. The name derives from a long piece of wood, the "tree", which could be placed over the harbor entrance to block off the harbor basin and thus prevent ships from entering if necessary. In front of the portal of the baroque building there are the so-called "Sweden heads", which in Swedish times marked the fairway of the harbor entrance on wooden poles.
(Source: information board on the building)

It houses a museum about the tradition of seafaring. There is a high water mark on the side.
The building is very centrally located on the port complex.