The entrance of the pit, surrounded by abundant vegetation, is funnel-shaped and in some places has vertical walls, but at the point where one arrives from the path there is a ramp that allows one to descend to the bottom of the said funnel (level – 6). Here, the shaft already presents a first vertical drop of 6 metres that allows one to reach a ledge that overlooks the entire main shaft. From the point of the ledge farthest from the entrance one can descend directly the 36-metre shaft, which is situated right in the middle of the lower level of the pit (level – 51.2). If one decides to descend below the entry vertical, one descends 6 metres more and enters through a window that gives access to a 27-metre shaft that is situated at the N end of the base of the main shaft. The gallery that forms the lower base of the cavity leads to a point where there is a descending crawl below a magnificent flowstone; once this passage is passed one reaches a small chamber (maximum depth level: 57.9 m) with an ascending chimney that communicates with the upper part of the flowstone.

A magnificent flowstone, below which is the descending crawl; an ascending chimney communicates with the upper part of the flowstone.

The entrance is funnel-shaped; a ramp allows one to descend to the bottom of the funnel (level – 6). The shaft presents a first vertical drop of 6 metres to a ledge that overlooks the entire main shaft. From the point of the ledge farthest from the entrance one can descend directly the 36-metre shaft to the very middle of the lower level (level – 51.2). If one descends below the entry vertical, one descends 6 metres more and enters through a window that gives access to a 27-metre shaft to the N end of the base of the main shaft. Following the gallery of the lower base one reaches a descending crawl below a magnificent flowstone; once this passage is passed one reaches a small chamber (maximum depth level: 57.9 m) with an ascending chimney that communicates with the upper part of the flowstone.

Toponymy: Many times we have heard the cavity called Avenc de les Pinasses, although at present the singular form seems more correct (Llopis in 1932 already calls it thus); it should be recorded, however, that Faura (1913) and in the Guia Monogràfica de Sant Llorenç del Munt (1935) call it Pinasses.

We update the record (April 2016) including two more surveys: the one made in 1932 by N. Llopis Lladó (Sota Terra II, 1935) and another, unpublished until now, made by members of the GES – CMB around the beginning of the 1970s during the work being carried out for the preparation of volume 3 of the speleological catalogue of the province of Barcelona that was never published. It should be noted that in the latter the maximum depth level is placed at – 62 metres.