This particular basilica is dated to the 12th century and is the former abbey church of a community of Benedictine Camaldolese monks (Ordo Camaldulensium). The Camaldolese monks were founded by St. Romuald at the turn of the first millennium. St. Romuald himself was formed originally under a very austere form of monasticism which had its roots in the strict eremetical and ascetical traditions of the Irish/Celtic monastic communities. Moving around Italy he established various colonies of hermitages that formed one half of the Camaldolese tradition. The other half is rooted in the cenobitic tradition of the Benedictines and it is this half of the Camadolese monastic family who made their home in the location we are looking at today.
If you were to visit the site, the medieval basilica is still standing with very little remaining of the monastic buildings proper -- though you can still see the footprint of the cloister along with its well located in its midst as well as a few other walls and arches from the other monastic buildings.
Readers will note the distinctive two coloured stone which is a combination of black volcanic rock (a closer look will still reveal the bubbles) and a lighter coloured limestone. This type of striped patterning is extremely beautiful and puts one to mind of the duomo of Siena.
The portico of the basilica continues this beautiful striped stone theme and includes some beautiful capitals with gargoyles and other foliage typical to the period.
The front facade includes beautiful geometric designs inlaid with coloured stone and ceramics.
Most striking are the frescoes -- dated to the second half of the 12th century -- within the apse and sanctuary depicting Christ the Judge, enthroned in majesty surrounded by angels. Below this level are situated the twelve apostles and the Blessed Virgin and St. Paul, and at the lower level are found various scenes of the life of Christ as well as a depiction of St. Benedict. (Readers may well observe how iconographic in form and content these works are, showing the common heritage of East and West that was still visible in the earlier middle ages.)