Below Rome's street level hides another city: early Christian catacombs, Roman mithraea, double churches and thousand-year-old aqueducts that few tourists know.
Underground Rome: the hidden world beneath the city
Rome has two faces: the one everyone knows, made of columns and domes, and the secret one hidden underground. Recent estimates indicate that beneath Rome there are over 900 km of tunnels, catacombs and ancient structures.
The Catacombs of San Callisto
The largest Christian catacombs in the world stretch for 20 km beneath the Via Appia Antica. Used between the 2nd and 5th centuries as a cemetery for over 500,000 Christians (including 16 popes), the catacombs of San Callisto are a moving journey into the history of early Christianity.
The guided tours (8 euro, limited groups) lead into the galleries where you can see the original niches, the early Christian frescoes and the crypt of the Popes. The internal temperature is constant (15 degrees C) - bring a jacket.
San Clemente: the layering of history
The Basilica of San Clemente (Via Labicana) is perhaps the most extraordinary site in underground Rome. Descending from the 12th-century church you reach the 4th-century basilica, and descending further you reach a 1st-2nd century Roman mithraeum dedicated to the cult of Mithras.
Three levels of civilisation in a single place: from Roman paganism to medieval Christianity. The aqueduct that still flows in the deepest part completes the picture.
Entry: 10 euro for the underground complex.
Domus Aurea: Nero's palace
The gigantic villa of Nero (68 AD), built after the great fire of Rome, extends beneath the Oppian Hill. Left unfinished after the emperor's death, it was covered with earth and used as foundations for the Baths of Trajan.
The guided tours with augmented reality (projectors on the ceilings that reconstruct the original colours) are a unique experience. Available only at weekends, booking required.