The Netherlands have long been known as a land of polders, tulips, and windmills. Switzerland may lack tulips, but its waterworks also look back on a centuries-old history of canalisation, the reshaping of river catchments, the drainage of peatlands, and even the lowering of lake levels.

Swiss watermills

At first glance, there seem to be no mills (apart from today’s wind turbines). But appearances are deceptive. The country has thousands of mills, but they are not easy to recognise from a distance. That is because they operate exclusively with waterwheels, powered by streams, waterfalls, and other waterways. From afar, they look like large or small farmhouses or warehouses—in reality, they are watermills.

Collection: Museum Les Moulins souterrains du Col-des-Roches

Underground watermills

In addition, innovative entrepreneurs in the 16th and 17th centuries built underground mills that were invisible to the naked eye. In 1555, underground waterwheels on Lac de Tallières (Canton of Neuchâtel) powered grain and saw mills. The underground waterwheels of the mills at La Ronde in La Chaux-de-Fonds were already in operation in 1489. The millstones and saws, however, were installed above ground. Both mill sites were decommissioned long ago (Lac de Tallières in 1923, La Ronde in 1870).

The history of watermills near Le Locle goes back to the 14th century. Le Gros Moulin in Le Locle dates from 1370; the Seigneur of Vallangin sold his mills in La Sagne, Brenets, and La Chaux-de-Fonds in the 16th century. Moulin de la Roche at the Saut-du-Doubs became the property of Daniel Sandoz (1604–1668) in 1642.

Fritz Huguenin-Lassauguette (1842-1926), lithographie, 1886. Collection: Museum Les Moulins souterrains du Col-des-Roches. Le Locle (on the right), the Col-des-Roches on the left.

The underground mills at The Col-des-Roches

The centuries-old mills at the Col-des-Roches, however, were built entirely underground in the 17th century, down to several dozen metres deep! The Col-des-Roches near Le Locle (Canton of Neuchâtel) is a rock formation that emerged over millions of years through the uplift of the Jura Mountains and the effects of seas, glaciers, and meltwater. Col-des-Roches is located about 2 kilometres from Le Locle.

Many caves and various streams have formed in the soft limestone of the Jura. This area was traditionally marshy and was only drained in the 20th century. In the 20th century, the stream Le Bied was partly channelled and still flows partly underground, before ending up in the Doubs at La Grotte du roi de Prusse in Lac des Brenets, near the Saut-du-Doubs.

Collection: Museum Les Moulins souterrains du Col-des-Roches

Famous visitors

The underground watermills were famous across Europe. Towards the end of the 18th century, the philosopher Karl Viktor von Bonstetten (1745–1832) put it like this: « les fameux moulins sont connus dans le monde entier”.

The mills and complex in the 17th century

The mills and complex in the 19th century

The name “roi de Prusse” refers to the Principality of Neuchâtel under the King of Prussia (formally from 1706 to 1857, even though Neuchâtel had been a canton of the Swiss Confederation since 1815 and a republic since 1848!).

In the history of the underground mills of Col-des-Roches, the name of the Prince of Neuenburg appears several times: as the grantor of milling concessions, as a visitor to the mills, and in connection with the regulation of the grain market. King Frederick William IV (1795–1861), also Prince of Neuenburg, visited the caves in 1842.

Various (European) politicians, writers, engineers, and other dignitaries also visited this “Wunder der Natur und Kunst” (as Frédéric-Samuel Osterwald (1713–1795) described it), among them the Venezuelan freedom fighter Francisco de Miranda (1750–1816), Prince Edward (1767–1820), Duke of Kent (the father of Queen Victoria), as well as Hans Christian Andersen (1805–1875).

The Heraldry of the Sandoz family. Collection: Museum Les Moulins souterrains du Col-des-Roches

Daniel and Jonas Sandoz

Daniel Sandoz acquired the milling concessions at Col-des-Roches, in what was then the municipality of Rochefort. His son, Jonas Sandoz (1626–1690), subsequently became the initiator of the underground mill complex in 1659, which included a grain mill, a sawmill, a threshing mill, and an oil press.

The Concession for Jonas Sandoz. Collection: Museum Les Moulins souterrains du Col-des-Roches

In the cave, he created spaces for five wheelworks, stacked vertically above one another along the waterfall of Le Bied. To do so, he had the cave excavated further and aqueducts constructed between the levels to channel the water. Each wheelwork was connected to a mill—or, in the words of the Conseil d’État of Neuchâtel in 1663:

“….il y puisse bastir et construire tels harnois et engins qu’il trouvera à propos, et qui luy soyent le plus commodes, utiles et profitables, soit moulins raise, rebattre, huilière, et autres artifices”.

The heyday in the 18th century

The owner did not operate the mills himself but leased them to millers. In their 18th-century heyday, this special and unique project still counted four underground mills. The watchmaking, textile, and lace-making industries ushered in a phase of industrialisation, prosperity, and immigration in the region, including Le Locle, La Chaux-de-Fonds, Val-de-Travers (asphalt mines!), and Cortaillod.

Demand for wheat and timber therefore grew enormously, but by the end of the 18th century, only three mills were still in operation. Madame de Gauthier, a refugee from the French Revolution, mentions in (Voyage d’une Française en Suisse et en Franche-Comté. Depuis la Révolution):

“Le moulin des Roches est situé à une quart heure de lieue du Locle dans une chaîne de montagnes, oû la nature a creusé une énorme caverne. Un ruisseau qui parcourt le vallon s’y précipite, et fait mouvoir aussi trois roues. Des escaliers taillés dans le roc, rendent ce voyage souterrain facile. Deux moulins servent à la mouture des blé ; le troisième au sciage des planches”.

The farmer collects the ground grain. Collection: Museum Les Moulins souterrains du Col-des-Roches

The end 

Over the centuries, various owners succeeded one another and introduced changes. The most far-reaching transformation was the installation of turbines in the 19th century. But it did not help. By the end of the 19th century, the era of the underground mills was over.

Maintaining the mills required substantial capital and labour; working conditions were very harsh. In addition, the cave’s humidity was not ideal for grain, so farmers had to collect their milled flour as quickly as possible. A roof was installed above the grain mills to keep dripping water and moisture at bay. The logs for the sawmill reached the wood mill via an entrance and an aqueduct.

The logs were transported along this chute to the sawmill

In the 19th century, new technologies (electricity and turbines) emerged, and water power quickly lost importance. New means of transport emerged (railways, cars). They transported and imported grain and timber cheaply and quickly over long distances, and the importance of local production and mills declined rapidly.

Around 1880, the mills ceased operation, but a new opportunity emerged: generating electricity. And in 1890, the first street lighting in Le Locle burned with electricity from a constructed 90-metre-high waterfall at the Col-des-Roches.

Museum Les Moulins souterrains du Col-des-Roches

At that time, however, the mills in the cave had already fallen into disrepair, and in 1899, the cave was given an entirely different purpose: it became a slaughterhouse. Because of the constantly low temperature (7°C), the cave was considered ideal for disposing of animal carcasses. This activity, too, was definitively discontinued in 1966.

After years of clearance work, the present-day museum opened its doors on 1 July 1987. It houses a permanent exhibition, temporary exhibitions, and a tour through the cave with its still-visible underground wheelworks and mills.

(Source and further information: Caroline Calame, Les Moulins souterrains du Col-des-Roches, Hauterive 2005; Museum: Les Moulins souterrains du Col-des-Roches).

New roads and the railway line from France to the Swiss Jura in the late 19th century. Collection: Museum Les Moulins souterrains du Col-des-Roches