Basilica di San Clemente

This 'lasagna church' offers a literal descent through time. At street level, you'll enter a beautiful 12th-century basilica with stunning mosaics. Beneath it lies a 4th-century church with faded frescoes. Descending further, you reach a 1st-century Roman house and a dark, atmospheric Mithraeum — a pagan temple dedicated to the god Mithras. You can even hear the sound of an ancient underground river still rushing through the lowest levels. It is a hauntingly beautiful experience that illustrates Rome's habit of building over itself. The cool, damp air and narrow stone passages provide a visceral connection to the city's multi-layered history that few other sites can match.