In the heart of Sant Francesc Xavier, beside the church square, hides the oldest religious building in Formentera: a 14th-century chapel whose construction was authorised in 1369 by the archbishop of Tarragona, Pere Clasquerí, dedicated to Saint Valerius, for the few inhabitants who remained after the Black Death of 1348. It is tiny: a single rectangular room with a barrel vault and bare stone walls. It was the island's only place of worship until the 18th century. It has been listed as a Cultural Heritage Site since 1993.