Why is there a tiny hole in the Bremen City Hall? Next to the Bremen Market Square. It leads through the wall inside the Bremen City Hall. The Bremen City Hall is one of the most important examples of Brick Gothic architecture in Europe. Since 1973, it is protected by the monument protection act. In July 2004 the building was added to the list of UNESCO World Heritage Sites.

I appreciate you help.

Here is a picture.

https://images.gutefrage.net/media/fragen/bilder/was-ist-das-fuer-ein-loch-im-bremer-rathaus/0_big.jpg?v=1521994132315