Les Moulins Souterrains du Col-des-Roches au Locle

Useful Information

Location: Le Col 23, 2400 Le Locle.
2 km from the center of Le Locle.
(47.049034, 6.721577)
Open: MAY to OCT daily 10-17:00, tours at 10:15, 11:30, 13:30, 14:45, 16:00.
NOV to APR Tue-Fri 14-17, tours at 14:15, 15:30, Sat-Sun 14-17, tours at 14:30, 16.
Closed 24-DEC to 02-JAN.
Fee: Adults CHF 14, Children (6-16) CHF 7, Students CHF 11.50, Seniors CHF 11.50, Family (2+2) CHF 30.
Groups: Adults CHF 9.50, Children (6-18) CHF 4, Students CHF 8.
Guided Tours: Guide (-15) CHF 50, Guide (-25) CHF 70.
Classification: SpeleologyKarst Cave SpeleologyRiver cave
Light: LightIncandescent Electric Light System
Dimension: T=7 °C.
Guided tours: self guided, D=50 min. Audioguide Français - French Deutsch - German Italiano - Italian English
Photography: allowed
Accessibility: no
Bibliography: Van der Paas, Jan Paul (1996): Underground mills at Col des Roches (NE), In: Speleophilately International, Schimmert (NL), Nr. 49, 1996, S. 26. Fig. N1824
Address: Fondation des Moulins souterrain du Col-des-Roches, Le Col 23, 2400 Le Locle, Tel: +41-32-889-68-92, Fax: +41-32-889-63-02. E-mail: contact
Ville du Locle, Secrétariat aux Musées, 2400 Le Locle, Tel: +41-32-9316262, Fax: +41-32-9318989.
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.


1652 concession granted by the Council of State of the canton of Neuchâtel.
1660 underground mills created by Jonas Sandoz.
1690 sold after he went corrupt.
1844-45 renovated and new mill erected by Jean-Georges Eberlé.
1884 facilities sold to the municipality of Le Locle by the Eberlé heirs.
1898 converted into slaughterhouses and used for health control when importing livestock from France.
1966 slaughterhauses closed down.
1973 start of development as a museum.
1987 opened to the public.
2001 museum and exhibitions space added.
2007 closed circuit for the water installed.
2018 courtyard beautified for events.


The valley of Le Locle and Le Col-des-Roches is swampy and flat, the Le Bied river is small and flows rather slow. But at the end of the valley it falls down a waterfall into a cave. The idea was to build the mill into the cave opening and use the height difference inside.

The Moulins Souterrain du Col-des-Roches (Col-des-Roches Underground Mills) originate in the year 1652, when the Council of State of the canton of Neuchâtel granted a concession to three millers to exploit the current of the river. They set up a mill with two cogs. Only a few years later in 1660 the operation was taken over by Jonas Sandoz, a wealthy heir to an influential family. He enlarged the site and installed cogs in the cave. However, after 30 years he was ruined and had to sell the mills in 1690. In the following years the owners changed frequently, until finally Jean-Georges Eberlé puchased the site in 1844. The baker from Le Locle enlarged and modernized the site and he was successful for decades. His heirs sold the mills to the municipality of Le Locle.

They used it for health control when importing livestock from France. The cave served as a dump for the carcasses of animals slaughtered for health reasons. This is obviously a bad idea, as karst water is not cleaned on its underground course. The cave was seriously polluted when the site was closed in 1966.

After a decade the worth pollution was gone and in 1973 renovation and cleaning began. The works took 15 years until it was finally opened to the public. Since then continuous extensions were added, like a museum and an exhibition space. In 2007 a closed circuit for the water was installed, which allows the demonstration of the wooden mills. As there is not enough water in the river, the water is reused by pumping it back up.

A factory in a cave! The underground mills of Col-des-Roche, are unique in Europe and a testimony to man's ingenuity and courage. On a 400 year old historical site 2 km from the centre of the town, visitors can plunge into an underground world to discover an astonishing use of hydraulic energy. Formerly, the water forced its way through the mass of limestone that blocked its path. Gradually, generations of millers hewed away the rock, dug wells and aqueducts so as to build, perfect and power an impressive system of hydraulic wheels, mills, paddles and saws. The history of these men is illustrated throughout the cave and in its museum.

Text by Tony Oldham (JUN-2001). With kind permission.