San Tommaso in Formis

San Tommaso in Formis is a church on Caelian Hill featuring a Romanesque entrance with a 13th-century mosaic by Lorenzo Cosmati. The structure integrates elements of the ancient Claudian Aqueduct into its walls, showing how Roman engineering was adapted for religious purposes.

Pope Innocent III transferred the church to the Trinitarian Order in 1209, a monastic community dedicated to helping freed slaves. This decision established its purpose as a center of religious mercy in the city.

The church displays a mosaic in its entrance showing Christ between two freed slaves, reflecting its historical mission of compassion. This imagery shows how the community understood the connection between faith and liberation.

The entrance is located at Via di San Paolo della Croce 10, next to the Arch of Dolabella near Villa Celimontana. The site is easily accessible on foot and sits in a quiet corner of Caelian Hill where you can move around freely.

Saint John of Matha, founder of the Trinitarian Order, lived in a small cell inside the Arch of Dolabella next to the church from 1209 until 1213. This direct connection between monastic life and ancient Roman architecture is something few visitors notice.