Well, not really caves....these sandstone mines were used 17th century to mine the sand to produce glass. After the land turned from French hands to the German government the French forces who occupied the area and the fortress above razed the castle, fortress and filled in the caves. The caves were lost to time and found again in the 19303 when children at play found the caves again. They are not open for tours year round. As the caves receive funding they continue to open more areas of the cave system...in 2015/2016 season they anticipate opening level 12 and 13 of the cave system. Admission was 5 Euros for adults and 3 for kids...or a Family card costs 11 Euros.
The framework shows behind my girls is a safety cage to protect visitors in the event that the sandstone breaks off. While you would think i detracts from the caves...it actually adds a very industrial almost gothic/steampunk edge to the caves. The posts and pillars seen are to hold the ceiling up and indicate if any movement of the caves has occurred.