Felsengänge (Rock - Cut Cellars)  

For centuries, numerous cellar vaults and passages were cut into the stone of the castle hill. Thus, because of the solidity of the sandstone below the castle, it was possible to create an extensive system of rock-cut vaults and cellars, sometimes comprising four storeys. There is documented proof that these subterranean vaults were used for the production and storage of beer as early as in 1380.

The mysterious subterranean passages, however, served only for the collection and transport of fresh water. Geological conditions in the castle hill are favourable for the collection of water, because rain water only seeps away slowly, forming "water horizons" above impermeable layers of clay, which can be found at various levels within the castle hill. Thus water could be tapped at comparatively small depths at various points.

During the war, many citizens also sheltered in the vaults during air raids.