Burgstelle Kybfelsen, Medieval castle ruins in Günterstal, Germany.

Burgstelle Kybfelsen is a medieval castle ruin set on a rocky ridge between the Günterstal and Kappel valleys. The remains include sections of walls and the foundation traces of a defensive tower.

A spur castle on the Kybfelsen is mentioned in Matthias von Neuenburg's chronicle from the mid-14th century, and the name "Kyburg" first appears in 1484 in the Weistum of Kappel. Finds from Otto Kantorowicz's excavations in the 1920s show the site was in use during Zähringer rule in the Breisgau in the late 11th or early 12th century, but who founded it and when is not established. Pottery from the 12th and early 13th centuries and the end of the castle in the first half of the 13th century are assumed.

The name comes from the Kyb rock, a natural formation that still defines the character of the spot today. Visitors who walk around the remains can see how the rock was incorporated into the layout of the fortress.

The site can be reached by marked hiking trails from both the Günterstal and Kappel sides. Sturdy footwear is a good idea since some sections are steep and the rocks can get slippery when wet.

A natural rock crevice runs through the site and acted as a ready-made defensive barrier, so no extra wall was needed on that side. The gap is still clearly visible today and gives the walk through the ruins a slightly unusual feel.