continuous changes and additions over time. See below
At the beginning of the 16th century a new structure replaced the earlier Rathaus. In the 17th century the building was enlarged and painted by Hans Bock with mock architectural features. The pavilion on the left was added on the left as well as the tower on the right were added in 1900. Wikipedia says that the decorative style is art nouveau. See below in the iron work in the central arcade.
The focus of the square
The central and earliest of the existing sections
Note the painted reclining figures in the spandreals of the arches as well as the decorative ironwork.