St Peter’s Church is one of the most important examples of romanic architecture in Sardinia.
This church is situated on the site of the former Bosa “Vetus”, the ancient roman settlement, near the left bank of the river Temo.
This place was settled in the Phoenician-Punican period and also later in the roman period, documented by roman inscriptions in the former church floor which existed until 1800.
The name “extra-muros” refers to the fact that the building is situated “outside the walls” of the new Bosa, today protected by the castle.
The church was built as a cathedral when the town became diocese in 1060.
After the construction on the Serravalle hill by the marquesses of the noble house of Malaspina, the population left the old settlement around the church and transfered their homes to the slope between the castle and the river.
The building is in the form of a basilica with a central nave and two smaller aisles
The ceiling of the central nave has a beam construction, while the lateral aisles form a transept.
The church was constructed after a long process in three phases: the first between 1062-1073, when the central body was built in Romanic-Longobardic style; in the 12th century were added the apse, the tower and the four bows at southwest. Then at north-west end and the facade was added, a work of cisterciensic monks in the gothic style with remaining Romanic elements, like the small temple on the top of the facades triangle.
Uniquely the architrave is made of white chalk while the rest of the facade is in red trachyte.
On it is shown, beginning at left and separated by simplified floreal ornaments: St. Paul, St. Constantine, St. Mary with the Child and St. Peter. Of interest are the rests of old downpipes representing with the symbols of four evangelists: St. Mathew (the angel), St. Marcus (the crowned lion), St. Lucas (the hoof of an ox) and St. John (the eagle).
In the interior of the church, on the pillar with the font, there is a latin inscription placed by the bishop Constantine de Castra, remembering the consecration of the building in 1073 (MLXXIII).
The two statues (St. Peter and St. Paul) are not original, the true ones (from the 17th century) are located actually in the new cathedral on each side of the altar.