Bonozorrotz IV

The entrance opens in an ascending vertical joint, leading by means of two plunge pools of 1.8 metres to a chamber full of beech leaves. In this area there are some small clasts. In its Southern part the chamber shows a crawlway, which leads to a vertical tube 4 metres high. This ends in a horizontal area at 3 metres' height.

In its Eastern part there are several semi-transparent columns, which mark the beginning of an ascending gallery that ends in a small window open to the outside. In the final horizontal area there are some lithogenic formations in the form of flowstone.

From the entrance, one ascends through a vertical joint and passes by means of two plunge pools of 1.8 metres to the chamber. In its Eastern part, the semi-transparent columns mark the beginning of an ascending gallery that ends in a small window open to the outside. In its Southern part, the chamber shows a crawlway leading to a vertical tube 4 metres high, which ends in a horizontal area at 3 metres' height.