The Balm ruins are the remains of a fortified cave dwelling in the Jura Mountains, in the municipality of Balm bei Günsberg. It is that canton's only cave stronghold and one of the few in Switzerland.
The stronghold was built 20 metres high in a natural cave of about 20 metres wide and 6 metres deep.
The outer wall was provided with two doorways and some narrow windows. The wet rock face was covered with a lining wall; and the rest was a simple two-story timber construction, which is shown evident by the presence of holes into which beams were inserted. While being restored, the presently visible wall openings were distorted from their original form. At a later stage in the building of the stronghold, a fortified, inhabited house with an inside width of 3.5 metres and a length of 29 metres was erected in the forecourt. Presumably this was a defensive fortification of some farming complex.
The entrance to the stone fortress stretched over a long, partly walled rise which is partly hewn from the rock. The connection between the forecourt and the fortress itself is still only incompletely reconstructed. The present-day rise is of modern source, and only partly represents its original state.
Excavations from the years 1939 and 1941 indicate that the place had been used as a habitation since early times.
References:The Gravensteen is a castle in Ghent originating from the Middle Ages. The name means 'castle of the counts' in Dutch. Arnulf I (918–965), Count of Flanders, was the first to fortify this place, building a medieval bastion on this high sand dune, naturally protected by the river Leie and its marshy banks. This bastion consisted of a central wooden building and several surrounding buildings, also in wood.
In the early 11th century, the wooden building was replaced by a stone residence, consisting of three large halls that made up three storeys, connected by a stone stairwell. The monumental stone staircase, the light openings, the fireplaces built into the walls and the latrines were signs of considerable luxury and comfort in those days. There was probably also a tower.