A labyrinth awaits in Germany's Devil's Cave

It may look like a gnarled tree stump with roots spreading in all directions but is in fact one of the countless stalagmites to be found at the Teufelshoehle (Devil's Cave) in Pottenstein, situated in the southern German region of Franconia.

This particular stalagmite has been growing at this spot for over 340,000 years and has reached a height of approximately 3.5 metres. Like the other unusual formations in the cave, it has become a major tourist attraction, drawing visitors from all over the world, dpa reported.

"The cave system is the largest in Germany and still hasn't been fully explored," explains Thomas Bernard, head of the local tourist office.

Each year, around 160,000 tourists make the trip to Pottenstein but, unlike the original potholers, they don't have to crawl on their bellies through mud to access the main g eological formations.

Instead, they use the specially constructed spacious pathways and stairs to explore the Devil's Cave, which is just one of over a thousand caves in the area.

Indeed the area has one of the highest cave densities in the world, caused by the fact that Germany's central mountain range, known as the Mittelgebirge, was covered by a warm, tropical sea 150 million years ago.

"That was an internal sea, which was not particularly deep, about as shallow as today's Mediterranean," says Bernard.

Sponges and micro-organisms settled on the sea bottom and created long reefs. As the sea retreated, over time the reefs became the limestone and dolomite cliffs and rocks of the Mittelgebirge, which have become a favoured location for climbers from throughout Europe.

Ground water rich in carbonic acid caused cracks and holes to form, leading eventually to the creation of the caves, which continue to develop to this day. "When rainwater meets the limestone, then the rock dissolves, creating crevices and caves," explains Bernard.

Water seeping through the ground creates the stalagmites and stalactites in the Devil's Cave, taking around 13 years to grow 1 millimetre. The journey into the heart of the mountain begins at the 14 x 25-metre-wide Teufelsloch (Devil's Hole), which locals also call the "gateway to the underworld."

In 1922, cave expert Hans Brand investigated a bit further and found a cave system stretching 3 kilometres into the mountain.

A year later, the first tourists began making their way through a 1,700m section of the cave, including the Barbarossa room, one of the three main caves where countless cones rise up out of the ground and what look like delicate icicles hang from the roof.

Visitors don't only see geological wonders in Pottenstein, the history of the region's cave bears is also documented. "These 400 kg bears used to live in these caves 30,000 years ago," explains cave guide Herbert Hofmann as he stands in front of a reconstructed bear skeleton.

Those who want to know more about the surrounding Frankische Schweiz (Little Switzerland) region, can find numerous activities nearby. For example, there is the cliff garden in Klumpertal, paddle-boating on the Schoengrundsee or a visit to the 1,000-year-old Pottensteiner Burg castle.