The cavity develops along a NNE-SSW joint that cuts a series of grey sandstones of marine origin, corresponding to the Calcina levels identified in the geological mapping (Berástegui & Losantos, 2003). In the first metres of vertical drop there is an intercalation of conglomerates and at the base of the cavity there is a level of marls. In the main chamber a small step of cm-dm order can be seen (sunken east block).

The entrance, a couple of metres high by one metre wide, gives access to a pronounced ramp almost 20 metres long. The inclination exceeds 40º and the floor is of sand and small pebbles, which makes the descent quite entertaining. The ceiling of the ramp remains horizontal from the entrance, which makes it gain height as we descend. Shortly before reaching the main chamber, we find on the left a small hollow through which one accesses the lower crawls of the North.

The large conduit of the main gallery is 41 metres long and develops towards the South, but turning slightly towards the West. The initial width is a good size, for it reaches 4 metres, although this lasts very little; as we advance it narrows rapidly to barely 2 metres, just where we find a large trunk placed expressly to access the upper level. If until now the ceiling seemed almost imperceptible to us, from this point we can follow it with ease.

For 16 metres, both the height of 2.5 metres and the width of 1.5 metres are almost constant. One can observe on the ceiling several holes that connect with the upper level, while the floor becomes flat, except for a small pit located at the end of the gallery, on the left side.

A right-angled fissure suddenly narrows the passage, at the same time as it reduces its height. The ceiling rises again until reaching 4 metres and 6 metres further on a pile of stones narrows the passage again. This time, the ceiling remains at the same level and it is the floor that drops one metre more suddenly, leaving us to continue for about 5 metres of gallery.

A stalagmitic formation in the form of a flowstone, which collects a 2 metre long pool where the main gallery ends.

It seems to be an ancient spring excavated following a marl stratum, like the Mentirosa de Monistrol, and which became dead when the torrent del Tortuguer was excavated.

Following the ramp down one must pass a short step to reach the main gallery. One must descend a half-metre step to continue the exploration.