One of the largest castle ruins is located in the municipality of Reith im Alpbachtal, directly on the national road near St. Gertraudi. It is the only castle with three towers. The advanced keep in the west, the Romanesque fortress with two keep towers, a round wall and the residential building (care home), once a gate tower. Kropfsberg was a border fortress of the Archdiocese of Salzburg. The first buildings were erected around 1147 and the palace was rebuilt around 1217. The first documented mention of the castle dates back to 1296.
The nursing home was only built around 1753. The middle tower was hit by a bomb in 1945, but later rebuilt. The current owners are the Dkfm family. H. Vogl-Fernheim. The castle, one of the most stately in the entire country, was built around 1200 or even earlier by the archbishops of Salzburg to protect their possessions in the Zillertal and was managed by castellans and keepers. The most striking features of the castle are its three mighty towers, originally crenellated and not habitable, of which the sophisticated and specially walled main tower shows particularly careful and regular stonework and the others were later raised with residential floors.