Grotte de Milandre

Useful Information

Location: Rte de Milandre, 2926 Boncourt.
(47.485679, 7.015975)
Open: closed.
Fee: closed.
Classification: SpeleologyKarst Cave
Light: LightIncandescent Electric Light System
Dimension: L=10,520 m, D=135 m.
Guided tours: closed.
Accessibility: no
Bibliography: I. Müller, W. Stiefelhagen, R.A.M. Intchi (1995): Réflexions sur les résultats obtenus par l'enregistrement en continu des pramètres géophysiques, électromagnetiques (VLF-EM) et magnétiques, pour l'exploration hydrogéologique des aquifères karstiques (Grotte de Milandre, Jura, Suisse), Bulletin de la société Neuchateloise des sciences naturelles, 118: 109-119.
Address: Grotte de Milandre, Rte de Milandre, 2926 Boncourt.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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1964 members of the Spéléo-Club Jura cross the sumps at the entrance and discover the cave.
1974-1978 40 m deep artificial shaft constructed to access cave.


The Grotte de Milandre is located near Boncourt, right at the border to France. It was named after the Tour de Milandre (Milandre Tower), the last remains of the former castle Milandre, which stands on a cliff above the Allaine river. This castle was built in the 13th century by the Earls of Montbéliard, but was destroyed 1674 by Marschall de Turenne after the Jura was occupied by French troups. The cave was developed around 1900 and was a show cave for some time. There were trails and staircases cut into the cave floor and railings. The guides equipped the visitors with carbide lamps. Later electrical light was installed. In the 1980s it was widely published in guidebooks, but in the 1990s it was closed and never reopened. At the moment the trails still exist but are damaged and the electric light is removed. The cave is closed and accessible only for speleologists through the local caving club.

The cave of Milandre is famous for its speleothems, and has also a cave river which is used for water supply. It is often mentioned as one of the longest cave systems of Switzerland, which is actually outdated. This cave is a big cave with a length of over 10 kilometers, but there are cave systems in Switzerland like the Hölloch and Sieben Hengste which are around 200 kilometers long. The sumps were first crossed by divers in the 1960s and during the 1970s artificial entrances into the rear system were built. The exploration quickly extended the cave to 10 km length, and it was the 4th longest cave of Switzerland for some time. Today, almost half a century later, it is still on place 11.

This cave was used for numerous scientific researches over the last decades. There are numerous scientific papers on the cave including cave climate, examination of the influence of cave tourism on the carbon dioxide level and so forth. Pretty close to Boncourt the trans Jura motorwas was built. It connects Belfort in France with Porrentruy in Switzerland, right across the Jura. But although it was rather likely that some karst features would be hit during the construction. It was known from the cave survey that the motorway would cross the cave at a point where it was covered by about 40 m of rocks. So it was necessary to do the construction with all necessary precautions. Both the construction of the motorway and a tunnel, and the use of the motorway afterwards had to be taken into consideration. This is one of the good examples how an organization of speleologists like the Schweizerisches Institut für Speläologie und Karstforschung (ISSKA) is able to help normal civil engineers in safe constructing in karst areas. They use this example to present their work in a well-made Worldbrochure.