San Crisogono: An Underground Paradise in Trastevere

The lower basilica of San Crisogono is a medieval jewel preserving extraordinary archaeological and artistic evidence whose dating is still under scholarly debate. To understand its importance, one must descend five meters below the present church and imagine Trastevere at the beginning of the 4th century.

Close to the port and the mills, and frequently flooded by the Tiber, the XIV Regio Augustea was the poorest district of the city, characterized by a lower-middle social class. In this area several Christian places of worship arose, foremost among them the titulus Iulii et Callixti and the titulus Caeciliae, built to create centers of gathering and assistance for the needy.

The titulus Crysogoni entered this social context at the beginning of the 5th century, when the cult of Saint Chrysogonus arrived in Rome from Aquileia through Pope Innocent I.

The hall of a 2nd–3rd century insula was adapted into a single-nave church divided by partitions separating the faithful from the presbytery. Three doors were opened in the north wall and the floor was raised by 30 centimeters.

In the second half of the 5th century the hall was extended to 50 meters and completed with an apse, a sacristy (secretarium), and a baptistery created from a late antique fullonica whose drainage channels remain visible in the annular crypt corridor.

Between the 6th and 7th centuries the building was structurally reinforced and decorated with frescoes arranged in two registers: a lower velum with a jeweled cross and an upper register with biblical scenes, including The Three Youths in the Fiery Furnace with the inscription VOTUM SOLVIT.

The most significant restoration was undertaken in the mid-8th century by Pope Gregory III, who raised the floor again, built a new presbytery with annular crypt, and implemented a new decorative program.

The crypt, still visible today, housed the relics of Saint Chrysogonus, Saint Agatha, and Saint Rufus. Frescoes depict the saints in regal attire symbolizing their heavenly glory.

A faux-marble decoration with porphyry and serpentine disks anticipates the later Cosmatesque pavement of the upper church.

In opposition to Byzantine iconoclasm, Gregory III promoted sacred imagery and supported Eastern monks, founding a Benedictine monastery beside the basilica.

The last artistic phase dates to the second half of the 11th century under Pope Stephen IX, with frescoes depicting Saint Benedict Healing the Leper, The Rescue of Saint Placidus, Saint Pantaleon Healing the Blind Man, and Pope Sylvester Capturing the Dragon.

These works mark a transition in Roman painting toward the Romanesque revival and represent the final artistic testimony before the basilica was abandoned in 1124, leading to the construction of the present church above.

The visit concludes by returning to the current church level, leaving behind the enchantment of a millennium still waiting to be rediscovered.