Altitude: 865m
Location: Above Rettenbachtal (north side); about 20-25 minutes on foot from Blaa-Alm.

A resurgence cave of major importance, visited by CUCC in 1976 and 2002. Krenmayr gives it 278m long, seasonally active, very roomy water cave. The associated perennial resurgence is Naglbrünndl, putting out 50-100 l/s.

Continue past the Blaa-Alm hostelry on the track to a crossroads of paths. Take the path to the right and then bear downhill and to the left at a fork by a small wooden hut. Follow the track until you end up walking parallel to the river; keep a lookout on the right for a small bridge across the river. Cross the bridge and take a small path to the left, which arrives at a further (smaller!) bridge over a stream. Just before the bridge, ascend up the hillside to the right through the undergrowth, keeping the large rocky gully to your right and the stream to your left. After a few minutes you will arrive at the resurgence (under tree-roots) to the left. At this point, cross into the gully on the right and climb up to the very top to reach the cave.

Entrance is at the head of a large, steeply-inclined stream bed (carries major flow in flood), and is reminiscent of Sleets Gill. A short climb (protection advisable; two hangers in situ; rope of unknown vintage present in 2002) leads to a tube. This descends at 45° to a short walk round a pool to a short greasy climb. One soon emerges in the huge main passage, floored at the lower end by vast amounts of very unpleasant mud. The sump is reached by a right turn over some fine stratified sand, but CUCC's interest lay in some holes in the roof at the top end, with the hope of a high-level continuation.

The mud eventually runs out to be replaced by more and more inclined slabs, which were very easy on the way up. The gradient steadily increases until the floor merges into the end wall, and the trickle of water enters from high up. At this point, a couple of holes in the roof have already been passed, but investigation revealed these to be beyond reasonable reach without some fairly serious bolting.

Exploration: LVHK Oberösterreich, 1972