San Francesco is the most architecturally intact medieval church in Alghero. The exterior is plain trachyte stone with a small rose window; the interior, late 14th century with later Renaissance additions, is mostly unadorned with the original ribbed vaulting still visible. The bell tower is a fine octagonal Catalan Gothic structure that the cathedral tower clearly imitated.
The reason most visitors come is the cloister behind the church — a small rectangular courtyard surrounded by simple stone arcades, with a single well in the centre. In summer it hosts the Estate Musicale Internazionale, a series of evening classical concerts (mostly chamber and choral) that the acoustics flatter beautifully. Even outside concert season the cloister is one of the quietest spots in the old town, free to enter during church opening hours.