Until recently, the late-antique castellum of Can Blai (also known as Can Pins) has not received the attention it deserves. Located in Sant Ferran de ses Roques in the centre of the small Mediterranean island of Formentera (Balearic Islands) (fig. 1), the fort was built at the highest (25 m asl) and narrowest point of the isthmus that joins the two major areas of higher ground, Puig Guillem on the north (107 m asl) and La Mola in the south (192 m asl). The fort lies c.600 m from the E shore and c.900 m from the W shore