The underground tomb of San Manno, an Etruscan artefact, is located in the western quarter of Ferro di Cavallo and is situated in the basement of the small medieval church of San Manno. The name derives from the owner of the church, for whom the hypogeum served as a crypt in Christian times. The plan of the hypogeum consists of a large main chamber and two smaller side chambers arranged symmetrically on the larger sides. All the chambers are barrel-vaulted, according to a type of burial that was widespread in inland northern Etruria from the Hellenistic period onwards. The dating of the hypogeum is controversial, but it is thought that it can be placed in the final decades of the 3rd century BC or at the end of the 2nd century BC.