L'Ajoie, près de Roche d'Or. Foto/Photo: TES.

The Ajoie, Dinosaurs and the Bishop

Porrentruy (Pruntrut in German, canton of Jura) was for a long time the seat of the bishop of Basel after he left his episcopal palace at the Münster in Basel during the Reformation in 1528.

The Bishop of Basel acquired this area in 999 by a gift of the (last) king of Burgundy, Rudolph III (977-1032). The king transferred the powerful abbey of Moutier-Grandval to the bishop. This abbey possessed the Ajoie and other territories in the Jura. The monastery was abandoned after the Reformation around 1530 and torn down to the last stone (Moutier and the Moutier-Grandval Abbey).

Porrentruy and Ajoie

Porrentruy is located in the Ajoie region, north of the River Doubs, on the edge of a plain in the Jura Mountains and a few kilometres from the French border. The large episcopal palace and castle on the hill, the Hôtel-Dieu, the glacière from the 18th century, the chapter houses and other grandeur bear witness to the centuries-long presence of this prince of the Holy Roman Empire of the German Nation.

The Prince Bishop and Bern

The bishop, also a prince of the Holy Roman Empire of the German Nation, hence the title prince-bishop and prince-bishopric, remained in possession of Ajoie until the invasion of revolutionary France in 1792. Only the Count of Monbéliard was lord of this region for a few periods, in 1283 and 1386-1461.

The prince-bishop definitively lost the territory in 1792. Ajoie, together with other regions of the present-day canton of Jura, fell under the short-lived Rauracian Republic (November 1792-March 1793), the department of Mont-Terrible (1793-1800) and the department of Haut-Rhin (1800-1813) before being annexed to the canton of Berne by the decision of the Congress of Vienna in 1815.

Many old boundary stones in the forests mark the ancient border of the canton of Bern (with Bear) or the Swiss Confederation (CS: Confédération Suisse) with France, marked with the French Fleur de Lille or RF (République Française). Since 1979, the French-speaking canton of Jura has formed the border with France.

Dinosaurs, Glaciers, Sea and Prehistoric park

Not only the bishop but also the dinosaurs, glaciers and sea are still visible. Some 20 million years ago, this region was situated on and under a subtropical sea. Further back in time, around 175 million years ago, the Jurassic was a favourite habitat of the dinosaurs. It was cold about 20 thousand years ago, with a polar climate with glaciers hundreds of metres thick and wide.

The Prehistoric park near the village of Réclère (Préhisto-Parc de Réclère) reconstructs the world of dinosaurs on a two-kilometre-long trail and a documentation centre. There are 45 lifelike replicas of the first fish, reptiles and dinosaurs on land, in the water and in the air along the trail. The 1,500-metre-long caves and their beautiful stalagmites and stalactites in this park were created in a process lasting millions of years.

The church of Réclère is also home to a more recent work of art: the famous stained-glass windows by Wilfrid Moser (1914-1997).


The name Ajoie is derived from the little Allaine, which flows through Porrentruy and into the Doubs. Other names for this region are Pay de Porrentruy and, in German, Pruntruter Zipfel (formerly also called Elsgau).

Mountains up to almost 1 000 metres surround the plain of the Ajoie. The agricultural use of the area is characterised by fruit trees, cattle breeding and arable farming, including rape and grain.

The hiker passes several ancient villages, such as Grandfontaine, above Réclère, Roche’d’Or, Rocourt and Chevenez.

The Swiss Alpine Club

The Swiss Alpine Club, section Basel (www.sac-basel.ch) regularly organises hiking trips in this region (and elsewhere).

The SAC (www.sac-cas.ch) organises ski tours, mountaineering and other sports in the high mountains and the Alps and activities in other regions.