The Zwehrenturm, a Gothic-style medieval gateway tower built in 1330, served as the town gate at the end of the Steinweg, the road leading to the south, in the direction of Frankfurt /Main. In 1709, Landgrave Karl commissioned the construction of an observatory with state-of-the-art astronomical instruments housed by a rotatable cupola, to be built into the top of the tower. This observatory enticed famous scientists to the Landgrave's court, such as Tycho von Brahe, Jost Bürgi (who devised his table of logarithms here in Kassel) and Denis Papin.

The lower part of the tower was temporarily used as a prison. In 1779, it was totally renovated and connected with the adjoining Museum Fridericianum (please refer to location Museum Fridericianum). The tower is graced by an escutcheon dating back to 1554 and a painted sundial from the 18th century.

As part of the Kunsthalle and the Museum Fridericianum, the tower's chambers today serve as exhibition rooms with a highly unique character.

Neighbouring locations:
Museum Fridericianum , Ottoneum / Museum of Natural Sciences, State Theatre Kassel,