A 12th-century church, on top of a 4th-century one, on top of an ancient shrine of Mithras - a walk through Rome's multi-layered history?

Even without its hidden depths, San Clemente is one of the prettiest churches in Rome with its 12th-century apse mosaic, The Triumph of the Cross, showing details of animals, birds and humans in flower-filled fields and its simple, 6th-century choir stall, originally in the earlier church building. The spiralling column next to the choir stall is a 12th-century cosmati mosaic candlestick. To the left of the entrance is the chapel of St Catherine with 15th-century frescoes by Masolini of her life and martyrdom on the original Catherine-wheel.