San Clemente displays the vestiges of history in a single building: at the lowest level an excavated apartment building with a Temple of Mithras; above that the lower church dating from the 4th century; and at the top level you can visit the upper church from the 12th century. You enter through a front courtyard with a beautiful fountain where summer concerts are held. Finely crafted mosaics adorn the triumphal arch and apse, and marble inlays decorate the interior.