The first church on this site was built in 939, when
Odo of Cluny was given the Roman palace of
Alberic II of Spoleto, which was then converted into a
Cluniac Benedictine monastery. The young
Hildebrand studied and took his first monastic vows here. When the monastery was dissolved in the 14th century, the site was acquired by the Knights of Malta, who had the church rebuilt in the 1550s. In 1760, the
papal nephew and Grand
Prior of the Knights, Cardinal
Giovanni Battista Rezzonico, sought to improve the appearance of the buildings. On a limited budget, the church was substantially renovated between 1764-66 according to the designs of
Giovanni Battista Piranesi. It is his only architectural work. According to a 2019 account, he "consolidated the structure of the 16th-century church and raised the side walls...restored the vault and designed the decoration for its new aspect". The keyhole of the Priory, at 3 Piazza dei Cavalieri di Malta, is famous. Looking through it, one can see a fantastic panorama of the dome of St. Peter perfectly framed by the hedges of the Priorato gardens. The keyhole was deliberately placed here, as part of Piranesi's design. ==Interior==