The Church is the most important architecture of the ancient town, situated in a very visible position which features thanks to its façade, the view of the ancient town. It was built, as Pope Sisto V desired, on the spot where he was born, on 13 December 1521, and is named after the patron saint of his birthday.

The first project was entrusted to Domenico Fontana and the building was started in April 1590: after the Pope’s death, in the August of the same year. Fontana was dismissed from the charge and the work was interrupted. The building went on for will of Camilla Peretti, Sisto’s sister, as reminds the inscription on the architrave over the portal and the medal preserved in the Sisto’s Museum, with Camilla Peretti’s effigy on the recto and the Church’s façade on the verso. The building was probably finished in 1595 and in 1597 was considered collegiate Church by Pope Clemente VIII.

The Church presents an essential and plain style, inspired to the rigorous principles of the Tridentine architecture. Over the portal there was the Peretti family coat of arms, today inside the Church, while it is still in its original place the Sisto ‘s papal coat of arms.

The choir over the portal has got an organ, built in 1752 by Francesco Fedeli, who went back to play in December, 2002, after an accurate restoration. Among the works preserved in the Church, it is worth remembering the altar dedicated to St Vincenzo Ferreri, adorned with a canvas portraying the Madonna with St Vincenzo Ferreri, commissioned by Pietro Ravenna in 1723 and recently attributed to the painter Ubaldo Ricci from Fermo.