The Church of San Pietro Barisano is a perfect example of the architecture typical of the Sassi: the façade is made of tufa, but the interior has been almost entirely hollowed out.
The church was built in the year 1000, when it was known as San Pietro in Veteribus, but the present façade dates from 1755, the year in which the church was restructured and partly altered, and there is an inscription to this effect.
The façade is made up of three architraved portals, of which the central one is the largest, two oval windows and an unusual quatrefoil rose window, all of which lend an air of great balance to the overall effect. The bell tower is separate from the main body of the church and rests on a base of natural rock. Its two storeys are separated by a terrace, its balustrade enlivened by a rusticated frieze, and it tapers as it rises, with a slim pinnacle at the top.
The church recently underwent some restoration, having been left abandoned and decaying after the general exodus from the Sassi during the 1950s, during which time it suffered at the hands of thieves and vandals.
The interior is comprised of a nave and two aisles, separated by imposing hollowed-out pillars that support round arches. There are six altars, all of which have also been carved out of tufa. The C18th main altar is of gilded wood.
In the right aisle a small opening near the first altar, dedicated to the Holy Family, is a space created during the C15th alterations that was later walled up for use as an ossuary during the C18th. It came to light during the latest round of restoration works and after the enormous quantity of bones found there had been removed, some ancient frescoes were discovered that had, paradoxically, been preserved by the walling-up process. On the jamb, the Face of the Virgin Mary and on the right: St. Catherine, St. Canione, an unknown Saint, St. Augustine, St. Eustachius and St. Roch.
The second altar along this aisle has a polychrome high relief of the Madonna and Child, with figures of saints in the side niches.
In the left aisle, the second altar, dedicated to the Annunciation, is worthy of note, with its sculpted group featuring the statues of the Madonna and the Archangel Gabriel.
The third altar has C176th - C18th sculptures and frescoes at the sides and is called the Altar of the Crucifix, after the brotherhood of the same name in Rome who venerated a crucifix that had miraculously escaped a fire that had destroyed the Church of S. Marcello in Rome in 1519. As the inscriptions at the entrance to the sacristy tell, its exposition conferred indulgence, as conceded by Pope Pius VI in 1777. Also in the entrance to the sacristy, the inscription “SANCTA SANCTORUM” indicates the entrance through the sacristy to the crypt, where there are two recently-discovered frescoes of Saints and another ossuary, as well as some characteristic “drainage” burial niches, so-called because the deceased would be placed there in a sitting position and, as his body decomposed, his bodily fluids would be absorbed by the porous limestone.