Schlossberghöhlen (Homburg Castle Mountain Caves)

The Schlossberghöhlen are a network of man-made caves carved into the red sandstone beneath the former Homburg castle, created gradually through centuries of quarrying for building stone rather than by design, and are recognized as the largest man-made sandstone caves in Europe. Extraction began under the counts who held Homburg Castle and continued in phases through the medieval and early modern periods, as successive builders removed stone from the same underground galleries to construct the castle above and buildings in the surrounding town. The castle itself was largely destroyed by French troops in 1679 during the Reunion Wars, leaving only ruins on the surface, while the excavated cave system below survived intact as it lay below the destruction. The caves maintain a constant cool temperature and high humidity year-round, conditions that shaped later uses of the space, including as a wartime air-raid shelter in the 20th century, evidence of which remains visible in some chambers. Guided tours today follow a marked route through the largest galleries, with information stops explaining the quarrying techniques used to cut the sandstone and the sequence in which different sections were excavated. The site's presentation emphasizes the caves as an industrial and construction artifact rather than a natural formation, distinguishing it from most show caves, which highlight geological rather than human history.