Carved in a natural trachytic amphitheatre dominating a fertile plain, Montessu is one of the most important prenuragic necropolises in Sardinia. It consists of about forty domus de janas tombs (literally “witch house” or “fairy house”), with different plan and dimensions. Two tombs in particular, considered as sanctuary-tombs for the cult of the ancestors, are impressive for their dimension and architecture: Sa Cresiedda (“the small church”) and Sa Grutta de is procus (“the cave of swine”), on the hedge of the rocky amphitheatre. They are characterised by a semicircle of megaliths on the front, 2m high entrances and a big pavilion used as vestibule, which leads through three openings into the tomb area. This last is divided by robust partitions whose closures are set in a spiral shape symbolizing the eyes. Two other tombs, not so impressive but very important for their religious symbology, are the so- called “spirals’ tomb” and “horns’ tomb”. They show rich carved or in relief decorations: red ochre “wolf’s teeth”, the colour of blood and regeneration, spirals which symbolise the eyes or the breast of the Mother Goddess, festoons, curvilinear and candelabra- shaped patterns, a false door to the afterlife, different shaped horns related to the Bull God cult. The necropolis dates back to the Late Neolithic age, the Culture San Michele di Ozieri (4th millennium BC) and was frequented until the Nuragic period (15th-10th century BC).