A very interesting and, for some aspects, quite surprising visit.
Basilica di Santa Cecilia in Trastevere is a titular church and minor basilica located in Trastevere, Rome. Dedicated to Saint Cecilia, the patron saint of music, it has served as a cardinal titular church since the 5th century. The present basilica, rebuilt under Pope Paschal I in the 9th century, is notable for its apse mosaic, frescoes by Pietro Cavallini, Baroque sculpture, and the revered relics of Saint Cecilia preserved beneath the high altar. Today, it remains the conventual church for the adjacent Benedictine abbey, and the feast of Saint Cecilia on 22 November continues to draw pilgrims, choirs, and musicians from around the world (text from Wikipedia).
A beautiful statue of the Saint (by Stefano Maderno) is placed under the main altar.
In a special room in a nearby (1st floor) building, there is a fresco about The Last Judgment by Pietro Cavallini, somehow surprising (have a look at the wings of the angels).

