Medieval archaeology and heritage of the Haut-Jura
Château de Chaux-des-Crotenay: fifteen years of excavations reveal the defences of a Jura fortress
To mark European Heritage Days 2026, we look back at the archaeological research carried out since 2010 at the Château de Chaux-des-Crotenay (Jura), which has uncovered a unique defensive system in the region, featuring fortified bridges and watchtowers.
Editorial journal · Carte des Châteaux ·
On 19 and 20 September 2026, as part of the 43rd edition of European Heritage Days, the medieval Château de Chaux-des-Crotenay will once again open its ruins to the public for a guided tour. Perched at 800 metres above sea level on a rocky spur in the Haut-Jura, this site, locally known as the 'Champ des Mottes', has been the subject of an archaeological excavation programme led by the ArchéoJuraSites association under the direction of archaeologist Stéphane Guyot since 2010. Over fifteen years of research have gradually revealed a defensive ensemble that experts consider one of the most distinctive in the Franche-Comté castle landscape, particularly for its unique moat-crossing system.
01
A site re-examined since 2010
As early as 2006, the medieval Château du Champ-des-Mottes stood out as a distinctive site in the Franche-Comté castle landscape. A study project was launched in 2010 by the ArchéoJuraSites association, a non-profit organisation founded in 1980 and active in the territory shaped by the Ain, Lemme and Saine rivers in the Jura. The project took concrete form in 2012 with a multi-year archaeological excavation programme, led by archaeologist Stéphane Guyot. Work has continued without interruption ever since: in 2018, ArchéoJuraSites created a dedicated committee within its board of directors, now chaired by Pierre-Louis Uny, a sign of the importance this site has taken on among the association’s programmes. A new publication on the château, written by Valbert Pique, was released in September 2025.
02
A strategic position on the salt route
The château stands at 800 metres above sea level on a rocky spur, about 500 metres south of the village, overlooking the Sainte-Marguerite church, a listed historic monument. Its precise date of construction remains uncertain, but some scholars place it shortly after 1186, the year when Simon de Commercy, a Lorraine lord who had received the barony of Chaux-des-Crotenay in 1170, built the nearby Château-Villain. Like the châteaux of L’Aigle, Nozeroy or Crillat, that of Chaux-des-Crotenay controlled access routes to the upper plateau of the Jura and Switzerland, including the salt roads, a strategic commodity during the Ancien Régime. The site witnessed several military episodes: besieged and occupied in 1639, during the Thirty Years’ War, by French, German and Swedish troops, it was retaken a few weeks later by the Franche-Comtois. After the definitive return of the French in 1674 under Louis XIV, the château was finally dismantled in 1691 on the king’s orders.
03
A bridge system deemed unique in the region
Excavations carried out between 2011 and 2016 uncovered several structures never before seen in the region. Archaeologists uncovered the piers of a bridge with a curved layout, as well as a gatehouse studied in detail during the 2015 campaign, whose design is considered unique: it featured a rear-swinging drawbridge, defended by two overhanging turrets resting on corbels. The official programme of the European Archaeology Days, run by the Ministry of Culture, confirms the discovery of a rotating fixed bridge and a rear-swinging drawbridge, described as unique structures in the region. According to ArchéoJuraSites, this crossing was also the only way to cross the dry moats surrounding the château.
04
Other elements of the fortress uncovered
Other areas of the site have also been documented. The access path and its paved road, studied between 2012 and 2014, follow the gentlest slope leading to the château. The barracks, among the most recent constructions on the site, housed the guards, their mounts and their weapons; they are linked to a parade ground set up in front of the château. The keep itself, the lord’s residence, was modified several times; a spiral staircase was identified and then reburied to ensure its preservation. The ramparts and a pierced tower, the last structure added to the site in the 15th century, allowed surveillance of the road along the foot of Mont Rachet, while a cobbled boulevard and a moat completed the defensive system. The excavations also yielded artefacts: fragments of glazed tiles, nails, 16th- and 17th-century coins minted in Dole, and two small couleuvrine cannonballs.
05
Why archaeologists continue to take an interest in it
Following these investigations, the Château de Chaux-des-Crotenay is now regarded as a reference site in castle studies. The excavation remains active: a field team, led by Pierre-Louis Uny with contributions from François Jacquet, Valbert Pique and Thierry Pasteur, continues the work, supported by the Jura Departmental Council and with the agreement of the site’s current owner, Katia Turnier. It is this ongoing excavation that European Heritage Days 2026 will allow the public to discover, with a guided tour organised on 19 and 20 September, meeting at the church car park and a 15- to 20-minute walk to the site.
Sources