Iberger Tropfsteinhöhle

Dripstone Cave of Iberg

Useful Information

Image: the café from the museum.
Location: In Bad Grund, 10km north of Osterode.
A7 exit Seesen (Harz), B243 towards Osterode until exit Bad Grund, at the B242 (Harzhochstraße) between the two exits to Bad Grund.
Open: JAN bis JUN Tue-Sun, Hol 10-17.
JUL, AUG daily 10-17.
SEP Tue-Sun, Hol 10-17.
OCT daily 10-17.
NOV Sat, Sun 10-17.
DEC Tue-Sun, Hol 10-17.
24-DEC closed.
During School Holidays in Lower Saxonia open every day.
Fee: Adults EUR 8, Children (6-16) EUR 6, Children (0-5) free, Students EUR 6, Disabled EUR 6, Families EUR 22.
Groups (10+): Adults EUR 7, Children (6-16) EUR 4.
HarzCard: free.
Classification: ExplainKarst cave, horizontal cave, Upper Devon
Light: electric, LED
Dimension: Entrance L=13m, Gelber Stieg L=77m, Klingebiel-Grotto L=11.5m, main cave L=123m, Spatzier adit L=78m.
Total: L=300m, VR=27,1m. T=8-9°C, H=100%.
Guided tours: L=220m, D=30min., St=136, VR=27m, V=62,000/a [2010]. (Deutsch - German English)
Bibliography: Dr. S. Kempe, F. Reinboth, F. Knolle ed. (1985): Die Iberger Tropfsteinhöhle bei Bad Grund (Harz), Hrsg.: Arbeitsgemeinschaft für Karstkunde in Niedersachsen e.V., Osterrode am Harz, 60 pp, 20fig., map, SB. (Deutsch - German)
Address: HöhlenErlebnisZentrum, Iberger Tropfsteinhöhle, An der Tropfsteinhöhle 1, 37539 Bergstadt Bad Grund (Harz), Tel: +49-5327-829-391, Fax: +49-5327-829-496. E-mail: contact
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.

Image: the new entrance building.


Middle Ages discovered during iron mining.
1734 first described by Brückmann.
1874 paths and stairs built, opened to the public.
1911 entrance adit built by Spatzier, survey.
1952 electric light.
1982 new survey.
11-JUL-2008 HöhlenErlebnisZentrum Iberger Tropfsteinhöhle opened to the public.
2012 LED light system installed.


Image: limestone quarrying on the Iberg.

The Iberger Tropfsteinhöhle (Iberg Dripstone Cave) was named after its location, it was formed inside the Iberg mountain (563m asl). The Iberg is a geologic anomaly, a small island of limestone surrounded by crystalline and metamorphic rocks. Like the other karst areas of the Harz it is a former reef of the Devonian sea. The organisms which formed the reef had skeletons and shells of limestone, the sediments which were deposited around the reef in the deeper sea are devoid of limestone. And like always in such small and isolated karst areas the limestone is karstified by water which flows on the surface until it reaches the limestone and goes underground. Containing little limestone it is able to dissolve a lot of rock thus forming caves. When it reappears at the lower end of the limestone area in a karst spring, it is saturated with limestone.

But there is a second extraordinary geologic feature of this small karst area. Generally caves are formed by atmospheric or biogene carbon dioxide, which is perceived by the water while it is raining down to the surface and while it seeps through the top soil. But here, the CO2 was produced locally, inside the rock, as a by product of siderite weathering. Siderite is an iron carbonate and is transformed into iron oxide and CO2 by the oxygen in the ground water. This CO2 increases the amount of limestone solution drastically. The residual iron oxide formed huge layers inside the caverns. During the Middle Ages the area was intensively mined, and the miners were looking for the so called mulmige Brauneisenerze (brown iron ore mold) inside the caves.

Image: a typical water mark on the cave wall.

A special detail of this mechanism are the specific water marks. The transformation of siderite into iron oxide was a continuous process, and so always a certain amount of CO2 was solved in the water and able do dissolve the limestone of the cavern walls, even if there was no supply from the surface. Because of this the water marks make sort of upside down steps, and the room becomes a little bigger below each water mark. In normal karst caves, water marks look more or less like horizontal ditches. The solution is restricted to the area around the water surface where mixture corrosion with dripping water dissolves some limestone.

The third specialty of the cave are coloured speleothems in one chamber, coloured blue green by copper minerals. In many karst areas, only iron oxides are available for colouring, and most formations look white to brown or sometimes yellowish or reddish. Limestone is a marine sediment, which contains only the minerals which are typically deposited in such an environment, iron and manganese. But if the limestone was alterated by a heavy tectonic action, like here in the Harz mountains during the uplift of the whole area, sometimes ores are deposited in the cracks. The whole process is started by the ascension of magma forming a plutonite, like the nearby Brocken mountain. The hot magma, stuck inside the earth, heats its surroundings and the ground water, which continually dissolves small amounts of various minerals and metals in surrounding rocks and re-deposits the ores in cracks. It formes polymetallic ores which were mined all over the Harz.

Image: the entrance adit, called Hauptmann-Spatzier-Stollen.

The caves of the Iberg were discovered by the miners of the Middle Ages. They mined the iron ore, used some to fill in overburden, then closed them and forgot about them. What later became the show cave was never forgotten, it was first mentioned in 1734, was shown to interested visitors, and finally in 1874 paths and stairs were built. This is the date when it became a show cave. At this time there was only one entrance at the upper end of the cave, almost unchanged since early mining. In 1911 a new 78m long entrance tunnel was built by Hauptmann Spatzier, and named after him. It became the new entrance of the cave, the old entrace was used as exit and the tour became a one way tour. It was even extended by a new cave discovered while digging the tunnel.

This way the tour stayed almost 100 years, in 2008 the cave was transformed again and renamed HöhlenErlebnisZentrum. Before the renovation the cave entrance was located above the parking lot in the wood, reached on a short walk uphill. The exit was even higher up on the hill. Both can be seen on the older images on the gallery page. The cave entrance is now located on the parking lot, where a two storey entrance building was erected. The ground floor contains the ticket office, a small shop, café and mineral exhibition. The second floor contains the archaeologic museum dedicated to the Lichtensteinhöhle which is a famous archaeologic site nearby and not open to the public. The exhibition includes a model of the cave, which gives a good impression of the original cave. It also show that the cave is actually rather small, the lowest point of the model is only 80cm high. Not suitable for every tourist, as it requires stooping and crawling, but great fun for children.

Image: new entrance tunnel with exhibition.

The cave tour was also changed, the cave is entered by a new constructed 160m long tunnel which leads up to the Hauptmann Spatzier Stollen. The tunnel is used for an exhibition showing the geologic development of the Harz, the limestone and the karst. It reaches the old entrance tunnel right behind the old entrance. Visitors take their time to walk uphill through this tunnel, have a look at the exhibition, and finally meet their guide at the Hauptmann Spatzier Stollen.

The first natural cave of the tour was discovered in 1911, during the construction of the entrance tunnel. There are some nice speleothems and fossils on exhibition, and also some speleothems on the ceiling. The driping water from the crack in the ceiling is collected in a small artificial pool. After the remaining part of the tunnel, the main chamber of the cave is reached at its deepest point. A wide staircase leads up to a first plateau, where the impressive watermark can be seen. The tour follows some side passages to meet the upper part of the main chamber. The main stalagmite is found here, called König Hübich (King Hübich), more about this later. Here is a steep and narrow staircase leading to the former exit, which is actually the oldest entrance to the cave. It is closed now, the visitors go back to the lower part of the main chamber and then back to the entrance through the tunnels.

Image: this formation is called König Hübich.

The Iberg Dripstone Cave is a historic show cave, and rather small. Despite the name, there are no extraordinary dripstones. The name was coined in the 19th century, at this time the name dripstone cave was used for any karst cave, it was actually more common. The most impressive formation named König Hübich (King Hübich) is a huge and massive stalagmite with a thinner and pointy tower on top, about 40cm high. If you know it, its easy to see that the slim top does not belong to this place. It is a part of another stalagmite, probably even a stalactite, which was placed here long time ago. There is water dripping at this place, depositing limestone, and so the top is today fused with the base.

Before Germany was united in the early 1990s, this was the only well developed tourist cave in the western part of the Harz. Then the much bigger caves of the eastern part became accessible and the importance and visitor numbers diminished. In order to stop this process, the cave was completely restructured and transformed into what is called HöhlenErlebnisZentrum Iberger Tropfsteinhöhle. The extensive renovation including the construction of a 160m long tunnel and the errection of a two storey building cost 3.85 Millionen Euro. It was financed by the European Union, the county Osterode am Harz, the Niedersachsen government, the Sparkassenstiftung and other foundations. It was executed by the county Osterode am Harz. The result is astonishing, almost 60.000 visitors during the first half year.

Iberger Tropfsteinhöhle Gallery