Want to escape Rome's crowds? Visit its underground sites.

Sprawling across the valley of the Colosseum and the Palatine and Esquiline Hill in central Rome are the remarkably well-preserved remains of Emperor Nero’s Domus Aurea, his so-called Golden House. Constructed after the Great Fire of Rome in 64 A.D., it covered at least 100 acres of the city and included landscaped gardens, vineyards, a banquet hall that supposedly rotated day and night, an artificial lake, and hundreds of rooms inlaid with gold, marble, ivory, and precious gems designed to catch and reflect sunlight.

It’s an ostentatious display of Roman engineering and imperial wealth, arguably one of the largest and most extravagant imperial residences ever built in Rome. Despite being a stone's throw away from the Colosseum, the Domus Aurea does not get anywhere near the same amount of hype as the massive amphitheater, even though it predates it by 16 years. Perhaps that’s because it’s located more than 30 feet underground.

Despite its subterranean location, the archaeological site is open to visitors. Only a portion of the entire domus has been excavated, as the majority of it is likely forever buried beneath modern Rome. The parts that are on display, however, are impressive to say the least. This underground site, buried over the millennia by successive emperors and the continuously evolving cityscape, is just one of several accessible, ancient subterranean monuments that lurk beneath the streets and chaos of modern Rome.

Spanning several centuries, they serve as a new window onto Rome’s layered past. On a more practical level, they offer a respite from the crowds and from the blazing heat in the summer months. From imperial residences and ancient apartment complexes to temples and private residences, these sites form what is, for all intents and purposes, a city beneath a city.

(Rome is teeming with mysterious crypts filled with popes—and secrets)

A city of layers

Since its inception more than 2,000 years ago, Rome has been built upon layers of streets, structures, and artifacts. It’s messy, confusing, and far from linear, but these various stratifications represent a continuity of life that extends from the 1st century B.C. to the present day.

The slightest foray beneath street level immediately brings you face-to-face with its past. That’s why whenever the city undertakes any kind of major construction or public works project—like the much-lamented C line of the subway system that has been in the works for two decades and is expected to be completed by 2034—there’s a delay related to archaeological findings.

“Rome is like a big lasagna,” explains Adriano Morabito, a speleologist and the president and co-founder of Roma Sotteranea, an association that holds educational courses, conducts research, and hosts guided tours of Rome’s underground. “From the moment Rome was born until today, it has grown in an irregular manner, with layers of stratification that occurred at different times. There are many Romes, one on top of the other, and each one was influenced by the one that came before it.”

A vast network

Rome’s underground is not confined to one area or one monument, but rather extends beneath the city’s historic center. Due to millennia of stratification, many of the city’s modern buildings are an echo of the past. The famous Piazza Navona square for example, located a five-minute walk from the Pantheon, owes its long ovular shape to the nearly 2,000-year-old ancient stadium found directly beneath it. Constructed in 86 A.D. and located nearly 15 feet underground, the ruins of Domitian’s Stadium can be accessed directly behind Piazza Navona. Tickets to explore the UNESCO World Heritage Site, the first and only masonry athletics stadium in ancient Roman history, cost around $10.

While difficult to quantify, Rome’s underground is likely as vast as everything we see within the Aurelian Walls—12-mile-long protective walls built in the 3rd century A.D. that encircle the city, including its seven hills. “It’s like a 3D puzzle,” says Morabito. “Of this puzzle, we probably only know five to 10 percent of the pieces, maybe even less.” As Rome has never stopped growing, the majority of these places are buried beneath modern structures and completely inaccessible.

A city of water 

Rome may be a city of layers, but it is also a city of water. It’s bisected by the Tiber River, and the area that now hosts the Roman Forum was once a marshy valley fed by the Tiber’s waters, (which allowed for a still-present underground population of ancient river crabs to call the area home). Today, water still plays a significant role in Rome’s underground. Beneath the imposing Temple of Emperor Claudius, constructed in 54 A.D. on the Caelian Hill, is a medieval-era tuff quarry, the foundations of a medieval monastery, and a series of wells and crystalline lakes pure enough to drink from.

This sliver of Rome’s underground is only available to visit with certain tour providers, and requires trekking shoes, flashlights, and hard hats. “It’s a unique, adventurous tour. You can have a speleological experience that teaches you that there is a lot of water beneath Rome,” says Morabito.

For those not so keen on adventure, the Vicus Caprarius, a small archaeological complex located about 30 feet underground, around the corner from the Trevi Fountain, provides a more relaxed view into this world. Also known as the City of Water, the Vicus Caprarius holds the remains of an imperial-age insula, an multi-story apartment complex that was later transformed into a luxurious private domus, and one of the collection and distribution cisterns for the Aqua Virgo, one of Rome’s 11 aqueducts. Built in 19 B.C., it’s the only aqueduct still in use today, and it feeds many of the city’s ornate Baroque-era fountains, like the Fontana della Barcaccia in Piazza di Spagna and the world-famous Trevi Fountain.

“It perfectly demonstrates the level reached by hydraulic engineering in Roman times, so much so that it still manages the flow of water perfectly, making some modern systems a little envious,” explains Lorenzo Dell’Aquila, the director of the Vicus Caprarius.

For centuries, this complex remained hidden beneath the city’s historic Cinema Trevi, which was abandoned at the end of the 1980s, says Dell’Aquila. It was only after renovations at the turn of the millennium that this fragment of Rome’s past came to light. Small, guided tours in English and Italian take place everyday for about $9. Through a system of suspended ramps and walkways, visitors can hover above the site, observing mosaic floors, terracotta amphoras that stored olive oil, and the cistern’s steady flow of water.

Domuses galore

The entrance to the Domus Aurea is located in the Colle Oppio Park, a 27-acre park that faces the Colosseum and abuts the Monti district. Guided tours in English, Italian, Spanish, and French cost $30 and are designed to gradually bring visitors into Rome’s underbelly. Some parts of the site are so deep underground that they require a sweater and jacket, even on hot summer days. Here, visitors will be guided through grottos complete with their original mosaic floors, pass through rooms boasting 30-foot ceilings emblazoned with frescoes, and weave between several banquet halls once complimented by extravagant water displays. There’s also a brief virtual reality tour of what the palace looked like in antiquity, including its expansive outdoor spaces and artificial lake, now the site of the Colosseum. 

There are also the Roman Houses of the Caelian Hill, situated beneath the Basilica of Saints John and Paul. The complex spans four centuries of Roman history and includes ancient workshops, warehouses, and private residences, including those that belonged to the Christian martyrs John and Paul. Guided tours are available for about $9.

(The ghost stories of ancient Rome—from the bone-chilling to the absurd)

In the basement of churches

One of the most common places to find traces of Rome’s hidden past is beneath its many churches. These subterranean sites don’t require reservations and access can be purchased on the spot as a ticket or an offering for less than $5. “They’re beautiful because you can descend a few stairs and go back in time,” says Morabito. Many churches will have signs for scavi (excavations) or sotteranei (underground) to lead visitors.

These underground sites, while smaller and lesser-known to both tourists and Romans alike, are nonetheless equally fascinating as the larger monuments because they “demonstrate how much history there is to discover even in less ‘famous’ context," explains Dell’Aquila. 

The 12th-century Basilica di San Clemente, a five-minute walk from the Colosseum, is one of the more popular examples. There are two layers to its underground: the first is the original medieval church, built in the 4th century, and the second is a series of ancient Roman ruins from the 1st century A.D., including a Mithraeum, public building, and a narrow alleyway.

There is also the 9th-century Basilica of Santa Cecilia in Trastevere, built upon the domus of Santa Cecilia, an early Christian martyr who was tortured and killed in her home in 230 A.D. About six feet below the current church lie the remains of her home, including geometric black-and-white mosaic floors, and her crypt, completely enveloped in marble and Byzantine-inspired mosaics. 

A new layer of Rome

Rome’s secret underground world is an opportunity to deepen our understanding of the city’s nearly 3,000-year-old history. It sheds new light on the structures that made up the fabric of Roman life over the centuries—whether it was private residences and multi-story insulas or imperial palaces and temples—where Romans, rich and poor, lived as we do today. 

Venturing into the city’s underbelly provides a snapshot of the city’s stratified essence beyond the Colosseum, Pantheon, and the other impressive monuments that have defined Rome for generations. It’s a reminder that there’s another world beneath our feet, and it can be found in church basements and below parks and bustling squares and administrative buildings.

“Rome was not only the splendor of the Domus Aurea, the sacredness of the Palatine Hill, the blood of the Colosseum, or the imposing architecture of the Campus Martius,” explains Dell’Aquila. “It was a city of houses, alleys, and shops … if we stop to reflect, history is nothing more than a gigantic puzzle of micro stories.”

(Where to eat in Rome like a local)