GeoRoute 9: Hike across the tropical Ruhla Island
This GeoRoute crosses the Rennsteig and together with its side trails is one of the longest in the Geopark. The trail starts at the Kittelstal Limestone Cave near Ruhla, crosses the Rennsteig and ends at Altenstein Cave near Bad Liebenstein.
However, 250 million years ago this walk through the forest would have been a diving expedition. Back then during the Upper Permian (Zechstein unit), Central Europe was located in the tropics. Tectonic processes had created a huge basin which connected to the superocean and became flooded around 257 million years ago. The result was a shallow tropical inland sea, the so-called Zechstein Sea. There were several islands in this sea including the island around the Town Ruhla. Over thousands of years reef-building organisms (esp. bryozoa and unicellular organisms) built gigantic reefs. One of these is the Altenstein Reef near Bad Liebenstein. This is not only the largest (approx. 1,6 km²) reef of the Ruhla Island, but also a rich animal fossil site from the Zechstein period. This is especially true for Altenstein Cave that was discovered in 1799. The cave is part of the landscape park at Altenstein Castle and provides a fascinating view of the inner structure of the Altenstein Reef. Just after it was discovered the geologist and palaeontologist E. F. von Schlotheim from Gotha identified the fossils as reef organisms and decribes the mountains as “prehistoric fossil reefs”.
Many more ice-age fossils where discovered during the further exploration of Altenstein Cave. This included bones from the cave bear Ursus spelaeus, which are thought to be 40,000 to 100,000 years old.
- Distance / Category: Main Route (Kittelsthaler Limestone Cave – Altensteiner Höhle): approx. 30 km, linear walk
- Side route (Circular trail Bad Liebenstein): approx. 20 km, Circular trail
- Side route ( Circular trail Ruhla): approx. 21 km, Circular trail
- Elevation: approx. 200 – 690 m above sea-level
- Difficulty: moderate – difficult
- Trail characteristics: forest roads, sandy gravel roads, paved footpaths in the towns, some asphalted sections
- Geological stations: Altenstein Cave (oldest and longest tourist cave in Thuringia), Limestone Cave Kittelsthal, Wartberge hills near Seebach with cutoff cones typical, historic blue dye factory Glücksbrunn (cobalt mine) in Schweina
- Touristic stations: Ruhla: Clock Museum, Miniature Park mini-a-thür and Adventure Toboggan Run, Thal: Scharfenburg Ruins, Schweina: Castle and Park Glücksbrunn, Bad Liebenstein: Castle and Landscape Park Altenstein, animal park and castle ruins
- Information: Tourist and Naturepark Information and GeoInfoCentre Ruhla, Naturepark Information Centre & GeoInfopoint at Altenstein Castle
Text: B. Aschenbrenner (PhD)