Seen from outside, it is a beautiful church dating back to the late 15th century, with its colours, the grey ashlars on the façade and the yellow plaster, that integrate nicely with the façades of the houses in the historic centre of Tuili and with the landscape at the foot of the Giara Park. However, the Church of San Pietro’s real treasure lies inside it: the majestic retable, the altarpiece created by the Master of Castelsardo. In reality, there is no certain information about the artist. It is assumed that he came from Barcelona and worked mainly in what was then Castel Aragonese, today’s Castelsardo. The work was commissioned by the feudal lords of Tuili, the Santa Cruz family, and carried out at the end of the 15th century. You can admire it in the first chapel to the right of the entrance, dedicated to the Madonna del Carmine (Our Lady of Mount Carmel): it is five and a half metres high and three and a half metres wide, the decorative pattern is the classic one used for altarpieces, with the Madonna with child in the central-lower section and the Crucifixion above. On the sides, there are images of saints, while episodes from the life of Saint Peter are depicted on the predella.