The Nature Reserve of San Juan Xar is located between the towns of Igantzi and Arantza. Ash trees, linden trees, oaks and hazelnut trees are the most common species. The Hermitage of Saint John the Baptist can be found in the reserve, which has an image of Saint Juan Xar inside, who was highly devoted to the area. It is popular belief that the spring water originating here has curing powers.

But most of all, this reserve gives protection to the hornbeam (carpinus betelus) a species of tree whose southernmost limit is found here. This is the only place in the Spanish peninsula where it grows naturally.