Dolmen San Martin

The burial chamber is polygonal and is formed of 10 large sandstone slabs. It measures 5.75 metres by 3.10 metres and has a maximum height of 1.90 metres. The corridor is almost 5 metres long, 1.20 metres wide and 1.30 metres high. It was covered with slabs, one of which remains. One of the five large slabs that form it carries a series of holes or cup marks of the kind found in megalithic art.

The mound, of stone and earth, measures 26 by 14 metres and is 2.15 metres high. Its northern part has disappeared, damaged by agricultural work in the field where it stands. The mound is estimated to have had a cover of white limestone from the nearby Sierra de Cantabria; this hypothesis rests on the fact that stones of that type still remain in the mound and in the shepherd's hut built over the dolmen, which rests on the north-western orthostats of the chamber and reuses stones from the mound.

The dolmen was located by José Miguel de Barandiaran and Domingo Fernández Medrano in April 1956 and was excavated by them, together with Juan María Apellániz, in July and August 1964. Several layers of stratification were detected. Two fallen slabs in the chamber sealed two distinct levels of occupation, one Neolithic and the other Chalcolithic.

After the excavation and study, the monument was restored: the fallen slabs were put back in place and mortar was placed between the orthostats. The only lintel still in its original position in the corridor was also secured.