The Trou du Creugenat is a karst hole in the Ajoie from which water emerges and which creates a temporary river, the Creugenat, during floods. The periodic lake forms between 4 and 10 times per year, the river is sometimes only visible for a few hours, sometimes over a week. The flow can reach 15 to 20 m3/s.
The water follows the Courtedoux plain and flows into the Allaine at Porrentruy.
When dry, the depth of the hole is clearly visible - simple steps lead to the bottom, and a thick rope helps you climb up or down. There is a water level gauge on the side of the rock walls and you can clearly see the mud traces of the last floods.
In the immediate vicinity of the hole there is also a picnic area with a table and benches, as well as an improvised fire pit.
A meadow path leads from the bike path to the hole.