Basilica of San Clemente al Laterano

The Basilica of San Clemente al Laterano is one of Rome's most architecturally and historically layered monuments, offering visitors a literal descent through nearly 2,000 years of the city's past. The current upper church, a fully functioning Catholic basilica administered by Irish Dominican friars since 1677, was built around 1108 CE by Pope Paschal II after the original church below was deliberately buried and used as fill to provide a stable foundation for the new structure. That buried church — the Lower Basilica — dates to the late 4th century, likely constructed during the pontificate of Pope Siricius (384–399 CE), and itself incorporated the walls of earlier Roman buildings on the site. Beneath both churches, excavated by Dominican prior Father Joseph Mullooly beginning in 1857, lie 1st-century Roman structures including a residential insula and a Mithraic temple — a sanctuary dedicated to the mystery cult of Mithras, complete with its original altar depicting Mithras slaying the bull (the tauroctony), dating to approximately the late 2nd or early 3rd century CE.

The upper basilica's 12th-century apse mosaic is widely considered among the finest surviving examples of medieval Roman mosaic art. It depicts a triumphant Cross rising from an acanthus plant that sends scrolling branches across the entire conch of the apse, populated with saints, apostles, peacocks, and scenes of daily life — a cosmic image of salvation rooted in the natural world. The nave is separated by ancient columns, many of them spoliated from earlier Roman buildings, and the schola cantorum — the marble enclosure for the choir — was physically salvaged from the 4th-century lower church and reassembled in the 12th-century nave, making it one of the oldest liturgical furnishings in continuous use in Rome. The Chapel of St. Catherine of Alexandria, painted between 1428 and 1431 by the Florentine artist Masolino da Panicale (and likely with the early collaboration of Masaccio), contains a fresco cycle that represents a pivotal moment in the transition from medieval to Renaissance painting.

Descending to the Lower Basilica reveals frescoes dating from the 9th to the 11th centuries, among the most significant surviving examples of pre-Romanesque narrative painting in Italy. One celebrated cycle depicts the legend of St. Clement himself — the third or fourth Bishop of Rome, martyred under Emperor Trajan around 100 CE — and includes a sequence illustrating the story of Sisinnius, notable for containing one of the earliest written examples of vernacular Italian (rather than Latin), dated to around 1000 CE. Deeper still, the Mithraic level carries the constant sound of an underground stream — an ancient Roman drainage channel still flowing beneath the city — which adds an atmospheric dimension to the archaeological experience unlike anywhere else in Rome.

San Clemente sits on the Via di San Giovanni in Laterano, a short walk from the Colosseum and within easy reach of the Lateran complex. Entry to the upper basilica is free; access to the excavations requires a separate ticket, which must be booked in advance through the basilica's website, especially during peak season. Visitors should allow at least 90 minutes to move through all three levels thoughtfully. The site remains an active parish, so Sunday morning access to the lower levels may be restricted during Mass. Closed footwear and covered shoulders are required throughout.