Aven de l'Ourtiset

The entrance is a 25-centimetre-wide by 30-centimetre-high crawlway that widens downward between earth and blocks for about 3 metres, followed by a vertical narrowing with dubious walls.

a sounder joint is descended by opposition for about 5 metres; at its base it is 60 centimetres wide on average. After a dynamited constriction begins the P l 1 (2.5 metres wide on average) with eroded and fluted walls.

After a low 'boîte aux lettres'-type passage (40 cm wide by 1.25 m long) opens the Puits des Crinoïdes (P44), on the edge of a slab; it is about 2.5 metres wide and divides into two parts. The arrival is on a wide ledge, with loose ground, spilling into the P20. An enormous block wedged between the two walls serves as shelter from possible rockfalls.

Towards the East runs a stretch of descending gallery strewn with slabs fallen from the roof; it ends in a joint shredded by dissolution, at elevation -77 m, no air.

The base of the shaft is covered with large blocks stacked over several metres, some of them unstable. a 6-metre step on an inclined plane is descended and emerges beneath the base of the shaft.

Advancing a few metres, one finds the P7, narrow at the start (0.40 m x 0.30 m) between slabs; it leads into sounder conduits (1 metre wide) temporarily incised. On one side, small potholes can be observed, filled with well-rounded pebbles, traces of downcutting. The bottom is close and ends in a fracture soon impassable at -111 m.

On the other side, one must traverse along a ledge (explained in the history) to reach the start of the Y-shaped P20. To reach the bottom safely, it is better to go via the South-west side.