The entrance to the main gallery of the Arenaza I cave, where the partially excavated site and the cave figures are found, is a relatively large opening which opens up to the west.
Beyond this entrance there is a large room containing the prehistoric site excavated since 1972, mainly by M. Apellániz.
Very little has been published with regards to this site. The publications refer mainly to the ceramics levels. Most of the Palaeolithic levels remain unexcavated. The ceramic levels date from Neolithic times to the historic era. Under these there are levels corresponding to the Mesolithic, and under this an Azilian level.
At the back of this chamber, around 30 metres from the entrance, there is a large gallery with an average width of around 20 metres and a height of more than 3 metres. Around 60 metres from where it begins, hence around 90 metres from the entrance, going up a ramp to the right (southwards), there is a low, narrow gallery, almost 40 metres long, at the end of which it is necessary to go down on one's knees in order to advance. It is very cramped, particularly in the end part which leads to the niche where the deer representations are found.
Continuing along the main gallery, around 80 m from the entrance to the narrow gallery which leads to the niche, hence around 170 m from the entrance, we find the aurochs section and, close to this, the female anthropomorph.