First, there was all the digging, for around five months, always on Sundays. That much his stepfather had granted. For the rest of the week, he had to slave away as usual in the quarry. But Johann Ziegler didn’t mind putting up with that. After all, he’d embarked on a daring undertaking.
Beneath the young man’s feet, there was a cavern. Ziegler had discovered it in October 1884, while working at the quarry. If his stepfather had his way, they would dig the cavern out. But Johann Ziegler had a better idea: he wanted to turn it into a show cave! His stepfather didn’t really like that idea. But he gave in, mainly because the lad threatened to sign up to a 12-year stint in the military.
On Whit Sunday in 1885, everything was ready. The Olgahöhle – Olga’s Cave – was opened for visitors. Württemberg’s government gazette described “a unique natural history phenomenon that is very well worth seeing”. Visitors enthused about the bizarre tuff rock formations.
Another ten years went by before people were genuinely able to appreciate the fascinating appeal of the cave. By then, visitors were no longer obliged to wander along the passages by candle light. The cave was equipped with electric light – at a time when cities like Reutlingen, Stuttgart or Paris were still in the dark.
In geological terms, Olga’s Cave is interesting because it’s not a karst cave. In other words, it wasn’t created by the limestone bedrock being dissolved – unlike most caves in the Swabian Mountains.
Instead, Olga’s Cave was created by calcium deposits. It’s what’s called a primary cave, since it was formed along with the surrounding rock during the last Ice Age – in other words, a mere several thousand years ago.
And this is how it happened: calcareous tufa was deposited on the edge of a waterfall on the River Echaz. That created a projection rather like a balcony. At the bottom of the waterfall, meanwhile, a wall of the same material was being formed - what’s known as a Kalkriegel. Over time, the two formations continued to grow, and finally merged, creating a void. The process was repeated several more times.
Among the typical features of Olga’s Cave are the dome-shaped formations of cyanobacterial tufa – also known as cauliflower sinter. As the cave was formed, these blue algae absorbed calcium and became fossilised. These days, the resulting tufa is in high demand as building material. In Honau, it’s part of the fabric of almost all the buildings, and the tufa rock was also used when Lichtenstein Palace was built.
Foto: © Wilhelm-Hauff-Museum