A visit of the 12th century Basilica of San Clemente with your local, English-speaking guide reveals a gleaming gold mosaic above the central apse. St. Clement's transformed over centuries from a private home that was the site of a secret Christian worship in the first century to an imposing basilica. What laid beneath the Basilica was unknown until 1860, when flooding led an Irish Dominican Roman Catholic priest and archeologist into the levels beneath the basilica floor.

Excavations are ongoing. Today, you can descend up to 100 feet underground over three levels together with your guide. At the first level we will find a 4th century Basilica, long forgotten after the construction of the 12th century Basilica above. Underneath, find the remains of an ancient pagan Mithraic temple. Lower still, ruins of ancient Roman homes.