San Pietro Extra Muros, Romanesque basilica in Bosa, Italy

San Pietro Extra Muros is a Romanesque basilica standing about one kilometer south of Bosa along the Temo River and features a reddish stone facade with large and small interlocking arches. The interior divides into three naves with a layout typical of Romanesque design, where the spatial proportions reflect the classic basilica form.

Bishop Costantino de Castra had the church built between 1053 and 1073 on a former Roman and early medieval necropolis; a carved stone in the north-east apse wall records the laying of the first stone. It was consecrated in 1073, as a second inscription above the baptismal font states. In the 12th century it was lengthened and widened, and the facade with its sloping gables is attributed to master Anselmo da Como in the late 13th century. Abandoned in the 15th century and deconsecrated, it was restored and reopened for worship in 1591 under Bishop Giovanni Francesco Fara.

The church is also known as Santi Pietro e Paolo, a double dedication that is not original: it comes from the statues of the two saints placed inside and dedicated in 1608. The name extra muros, common in local usage, has no basis in old documents and better fits Sant'Antonio Abate, which actually stands just outside the town walls.

The church stands in open countryside at Calameda, on the left bank of the Temo about two kilometres from Bosa, so it is reached by road rather than on foot from the centre. The first stone was laid by Bishop Costantino de Castra, probably in 1053 or 1062, and the building was consecrated in 1073; two inscriptions, one on an apse lesena and one above the baptismal font, record these acts.

On the north-east side of the apse, a stone block of a lesena bears the inscription recording the laying of the first stone by Bishop Costantino de Castra, probably in 1053 or 1062. It is the oldest epigraphic date from the Judicate of Torres. A second inscription above the baptismal font in the central nave records the consecration in 1073.