With so much to see above ground, many travellers never venture into Rome’s crypts and caverns where underground rivers, ancient frescoes and the temples of forgotten cults wait. By Alexandra Turney.
Beneath the streets of Rome is a hidden city. It’s a city of underground rivers, temples and burial chambers. When I’m on the metro, speeding – or, more often than not, crawling – through the city centre, I imagine the bodies buried nearby, bones rattling to the vibrations of the train. Walking through the quiet residential streets of the Aventine Hill, I experience momentary vertigo as I remember what lies underground. If I opened the manhole cover, I would fall into a vast cave, once part of a complex of Roman quarries.
The churches have their secrets too. Many people walk past San Clemente, a church close to the Colosseum, without giving it a second glance. Rome is full of churches, after all, and once you’ve seen a few relics, mosaics, and the usual paintings of the Virgin Mary, you might think you’ve seen them all.
But San Clemente is no ordinary church. The twelfth century basilica sits on top of the remains of two earlier churches, and the ruins of a Roman house and a mithraeum. On an Underground Rome tour with Through Eternity, I descend into the depths of the church and discover another world.

The first underground level beneath the church is huge, dark and disorientating. Once a fourth century church, it is now a subterranean ruin, sandwiched between the twelfth century basilica and the house of a Roman nobleman. Most of the walls are bare, but there are a few faded frescoes that hint at a former life. On one wall Saint Clement performs a miracle, rescuing a young boy from his underwater church in the Black Sea. Crossing the church I find a shrine to Saint Cyril, the inventor of the script that would one day become the Cyrillic alphabet. He was once buried here, but now only a fragment of the relics remains. The disappearance of his body is one of the many mysteries of San Clemente.
The deeper levels are stranger still. Peering through the railings I see a small mithraeum, a cave-like temple that was built in a Roman house. Mithraism was once a rival to Christianity, another religion that tells of the triumph of good over evil, with a promise of salvation. The gloomy little temple beneath San Clemente offers a tantalising glimpse of this mysterious religion. All that remains is an altar, depicting the hero Mithras killing a bull. We’ll never know exactly what went on during mithraic ceremonies, but the marble altar in the cave suggests secret initiation ceremonies and sacrifices.

Those who suffer from claustrophobia might not want to linger for too long in the narrower tunnels of San Clemente. But just as I start to crave daylight, I hear an unexpected yet unmistakable sound – running water. The sound is surreal, almost eerie, and for a moment I wonder if my mind’s playing tricks. Then I turn the corner and discover an underground river. This humble stream of water once flowed into the lake of Nero’s palace. The lake no longer exists, as it was replaced by the Colosseum, but deep underground, the river flows on.
A church on the nearby Caelian Hill hides some very different ancient ruins. After the gloom of San Clemente, the underground level of Santi Giovanni e Paolo seems brightly lit and cheerful. I feel as though I’m walking through a small subterranean city, complete with original Roman streets. I explore the remains of an insula (a Roman apartment block) and a domus (a spacious Roman house), which now resemble a maze of painted walls. Colourful frescoes feature the pagan imagery that was so common in early Christian art – vines, astrological symbols and mythological figures. One wall of an underground courtyard appears to show Proserpine reunited with her mother, Ceres, during a brief respite from her life in the underworld. Bacchus pours her a drink while cherubs sail around them.

Two Roman soldiers, John and Paul, once lived in one of these houses, until their martyrdom in the fourth century. Very little is known about them, or any of the other occupants of the residential complex, but as I walk through the underground rooms and streets I feel some kind of momentary connection with the people who lived here. Even if I don’t know their names, it’s enough to admire the frescoes that decorate their homes, and to see that the Romans were not so different from us. Like us, the Romans valued beauty, and wanted to be surrounded by images that gave them a sense of well-being. There’s little difference between the frescoes of the underground houses and the photos, paintings and posters that we display in our own, modern-day houses. Art makes a house a home.
Going underground in Rome can be an unsettling, disorientating experience, as I’ve discovered in places such as the mithraeum of San Clemente or the macabre Capuchin Crypt (a series of underground rooms filled with thousands of skeletons). But there are moments in the underground city when you suddenly feel close to the people who lived, prayed and died in these rooms. Underground Rome is not as dark as you might expect. Look carefully and you’ll see the colours, shining a light into the past.