The entrance, lateral in form, gives way to a 34 metre pitch that widens towards its base, covered by a considerable thickness of chough guano, as is the ledge located at the –17 level, slightly offset from the vertical. At the E end of the bottom of the pitch, by means of a small step and a narrow passage, one enters a second vertical of 21 metres, reaching the –63 level, where to the volume of this second pitch is added that of a blind-vaulted cavity located at the SW end. A third pitch, elongated in form, with a drop of 9 metres, gives way to two small pitches and at the bottom of the larger of them the maximum penetration level was reached until 2008 (-83 m, GEB survey revision).

About 4 metres from the last pitch of the pit there is a window which, once passed, allows entry into a bottomless meander (Meandre Arele), which little by little gains depth (at some point it exceeds the –100 level) and at the middle of its course presents a chamber of larger dimensions (Sala de la Colada). In the last stretch, the meander climbs a little and connects with a 32 metre pitch (Pou de les Nogueres). At the middle of this, by climbing, one can reach a chamber located in the upper part (Sala de les Excèntriques). At the bottom of the Pou de les Nogueres there is a really very narrow passage (Pas de l'Àngel) that allows entry into a new vertical, of 32 metres, at the bottom of which (level –166) the progression currently ends.

New branches have also been explored in the 'old' zone of the pit, notably a lateral zone in the middle part of the entrance pitch. Following the exterior fissure and about 50 metres higher up, the members of the GE Badalona were able to clear the mouth of a new cavity (Avenc Superior) and in which they were able to descend to a depth of 20 metres. Everything seems to indicate that it may be directly related to the grallera, but for the moment the passage between the two is not possible.

The walls of the second pitch are draped with magnificent flowstone. The base of the third pitch is covered by a stalagmitic crust.

The progression described is as follows: lateral entrance, 34 metre pitch, ledge at the –17 level, second vertical of 21 metres down to the –63 level, third pitch with a drop of 9 metres, two small pitches and bottom of the larger one (maximum penetration level -83 m until 2008). About 4 metres from the last pitch there is a window that leads to the Meandre Arele, which gains depth (exceeds the –100 level) and presents the Sala de la Colada; the meander climbs and connects with the Pou de les Nogueres (32 m). At the middle of this pitch, by climbing, one reaches the Sala de les Excèntriques. At the bottom of the Pou de les Nogueres is the Pas de l'Àngel, which allows entry into a new vertical of 32 metres and at the bottom of which (level –166) the progression currently ends.

Toponymy: Although for many years the words graller and grallera have been mixed and used interchangeably, it seems that the most correct would be, and thus Joan Coromines confirms in his Diccionari Etimològic i Complementari de la Llengua Catalana, that the word grallera would be the correct one throughout the Pyrenean zone from the Llobregat to the Segre, and from there westwards the term graller would prevail (starting from the most common: lo graller). Curiously, when we go into Aragonese lands and from the Éssera basin onwards (not in the Franja, which continues to use graller), the toponym grallera is used again.