The Itxina massif is found within the Gorbeia Natural Park and represents a key element in its landscape. It comprises a large outcrop of limestone of the Urgonian complex, formed by coral reefs that grew in shallow seas 110 million years ago.
Rainwater dissolves the rock causing depressions (dolines) and breaks up the rock in the form of grooves and channels (lapiaces). These are the so-called Karst formations. Among the most noteworthy of these is the famous Ojo de Atxulaor, the central Gran Grieta, the Axlaor doline and the Supelegor cave.
The filtered rainwater forms a large, enclosed subterranean basin that feeds the main spring, which is called Aldabide, to the north of the massif. One peculiar feature is the use of some of the deep Karst cracks as refrigerators to keep snow well into summer. In fact, in Itxina, one of these, in Neberabaltz, is in perfect condition.
The flora in the Park is extremely varied and is of great interest to moss experts. There are more than 175 species of mosses and catalogued hepatics. One aspect which has contributed to this abundance of species is the large amount of rotting wood in the Park, something which is difficult to find in other places in the Basque Country due to the massive forestation in this region. This wealth of flora is increased by the presence of singular species on the crests and vertical rock faces. Some beech trees grow in the harshest and most unexpected places and today there is still evidence of the use of these trees for producing charcoal.
With regard to fauna, one curious detail is that there are at least eight species of bats. In years gone by, these animals were associated with witchcraft and evil practices, but they are beneficial to man as their main diet consists of insects.