Gallura's most important Romanesque church is dedicated to Olbia's bishop and patron saint, the martyr San Simplicio, who was persecuted by Emperor Diocletian (4C). Built out of granite in the 11C, the basilica has the particularity of presenting a west-facing apse (most face east). Inside, the three naves are separated by arcades. The decoration on the capitals is quite basic, as granite is a difficult material to sculpt.