In these valleys of Navarre it is recovering as an ancestral tradition the coalfields that were built in the past in the forests of Leitza. This technique was used as a way of life, to extract the coal that was then sold to local producers and artisans. Construction of wooden mounds, in the center is left gap for chimney through which comes the smoke of the wood ember that turns into coal. The process that must be monitored takes up to several days.