The castle's Witches' Tower (Hexenturm) is one of the town's oldest buildings and a substantial local landmark.

In the early 17th century, during the time of Prince George Augustus Samuel of Nassau-Idstein, a Renaissance style schloss was built on the site of the outer ward.

The architect was Maximilian von Welsch, the stucco work, especially in the so-called Emperor Chamber (Kaisergemach), was carried out by Carlo Maria Pozzi.

The nickname became widespread around 1900 with the publication of Die Pfarrfrau von Heftrich by Ottokar Schupp [de].

[4] At the base of the tower is a plaque in memory of the victims of the witch trials of 1676, listing the names of 31 women and 8 men[5] killed at the end of the rule of John, Count of Nassau-Idstein.