Discover Rome’s Secret Underworld: A City Beneath the City

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“Be cautious of that bat behind you,” cautioned Luca Messina, a civil engineer by profession who also works as a speleo-archaeologist with the Sotterranei di Roma, a group dedicated to exploring Rome’s underground. As the bat darted past my ears, I shifted my headlamp’s beam to ward off unexpected encounters with the local wildlife. “Don’t let the insects bother you,” Messina gestured towards the ancient walls, now home to spider-like crickets known as Dolichopoda. “They’re harmless.”

We found ourselves in the dark, echoing depths of the Aqua Anio Vetus, a well-crafted aqueduct that commenced construction in 272 B.C. and had been dry for nearly a millennium and a half. For many, this subterranean environment might inspire fear or unease. However, for me, it ignited a fascination with Rome’s less visible history and secrets.

That morning, I had gathered with half a dozen fellow adventurers for coffee and pastries at a bustling metro station in the city’s eastern reaches. With cheerful banter, we prepared ourselves with hard hats and headlamps, while some donned steel-toed boots and protective overalls adorned with the emblem of our group, a stylized outline of an ancient amphora. A short drive led us to the surprisingly verdant Roman Campagna, where we hiked across expansive fields dotted with tall grass and purple flowers, utilizing scythe-like tools to clear our path. “Just 20 minutes from Rome, and it feels like we’re in the Amazon,” Messina joked.

As we passed through the overgrown arch of the ancient Taulella Bridge, the group’s focus shifted towards the ground. While Roman aqueducts might typically be envisioned as grand, above-ground monuments—especially prominent in places like the Park of the Aqueducts—most of their passageways are actually underground, designed with a slight gradient to leverage gravity for water flow.

The 600-acre Park of the Aqueducts, famous for its picturesque ruins, attracts both locals and tourists seeking a respite from the hustle of central Rome.

Over the had five centuries, from 312 B.C. to A.D. 226, eleven remarkable aqueducts were constructed to channel water into ancient Rome. However, ten of these were severed during the Gothic siege of A.D. 537, leaving a tangled maze of tunnels beneath the modern landscape that remains largely unmapped. The quest to unearth them has drawn eccentric explorers since the Renaissance, fueled by an interest in classical antiquity. British archaeologist Thomas Ashby conducted extensive research on these structures between 1906 and 1925, producing a significant work titled The Aqueducts of Ancient Rome, published posthumously in 1935 by his wife. Today, Messina and fellow speleo-archaeologists expand on Ashby’s pioneering work using modern technology.

“Ashby documented many of the aqueducts, but without GPS, his references to landmarks can often lead to confusion,” Messina explained. “Many of the sites he described no longer exist—farmhouses are gone, roads have changed, and buildings have fallen to ruins.” Today, their efforts focus on pinpointing Ashby’s findings using GPS and making this data available on platforms like Google Earth.

After about 20 minutes, Messina discovered a cippus—a stone pillar, typical from the era of Emperor Augustus, marking the aqueduct’s underground route. “There are thousands scattered throughout the countryside,” he stated. “We can only guess how many are out there.” Nearby, a concealed hole surrounded by foliage led to a vertical shaft that once allowed Roman maintenance teams, called aquarii, access to the aqueducts. Messina remarked on the issue of calcium deposits affecting water flow, comparing aqueduct maintenance to upkeep on espresso machines.

Utilizing a portable wire ladder, the group descended into the 25-foot vertical shaft where we found ancient footholds carved into the stone walls. As we cautiously made our way about 80 yards into the tunnel, we experienced il oblio, the Italian term for “oblivion.” The air grew stale in the dimness, creating a sense of unease. We scuttled over rubble where parts of the ceiling had collapsed. “It’s quite safe,” Messina assured, “There’s only been one collapse in 2,300 years—we’d have to be very unlucky.” He proceeded to map the area with a hand-held 3D scanner, indicating that we could eventually emerge at Rome’s Esquiline Hill.

The descent into the Anio Vetus was a unique discovery experience in a city known for its crowds and historical attractions that have drawn pilgrims, artists, and modern tourists alike for centuries. Having embarked on my first visit to Rome two decades earlier while researching ancient tourist behavior, I assumed I had explored all key historical landmarks. Yet stepping into the aqueduct revealed an entirely new, hidden realm beneath the bustling city—a reminder that Rome holds countless forgotten stories, waiting beneath the surface for those daring enough to uncover them.

In fact, amidst the ancient ruins such as the Colosseum, the Pantheon, and the Temple of Saturn, one notices that these structures stand well below the current street level. Since the fall of the Western Roman Empire in the fifth century, the ancient city has gradually been buried under approximately 30 feet of urban development and muck, much of which remains unseen. The resulting underground labyrinth has made Rome notorious for sinkholes, frequently swallowing vehicles whole; in fact, it has been dubbed “the sinkhole capital of Europe” by the Times of London. Yet, this very phenomenon has given rise to a new breed of enthusiasts—speleo-archaeologists—who are eager to work alongside academics to create a thorough map of how the ancient city has unfolded over three thousand years. This fascinating endeavor unveils a honeycomb of hidden landscapes, consisting of pagan temples, public baths, concealed lakes, nymphaeums, extensive sewer systems, mining tunnels, and ancient burial grounds. As one scholar succinctly put it, this represents the final frontier of Roman archaeology.

“Many think of ancient Rome as a lost civilization,” advised Giuseppina Mattietti, a geoscientist from George Mason University. During our lunch on Isola Tiberina, she emphasized, “But the reality is not so; it remains—Romans simply built on its remnants for centuries.”

Mattietti, who was born in Rome and has lived in the U.S. for over 30 years, has participated in numerous underground expeditions with Sotterranei di Roma over the past decade. These escapades have ranged from navigating the tunnels beneath Palatine Hill to traversing the Cloaca Maxima, the ancient sewer system lauded by first-century scholar Pliny the Elder as a testament to engineering prowess, which continues to be part of the modern city’s infrastructure. “I needed a full hazmat suit and vaccinations against hepatitis, cholera, and a dozen other diseases,” she recalled. “I took every precaution.” I heard tales of her experiences involving wading through powerful water currents in the sewer, maneuvering using digging sticks in mud to avoid being swept away.

The hidden spaces beneath Sts. John and Paul Church also reveal surprises for audacious explorers. The site, once quarried for tuff until the fourth century A.D., transformed into pools of breathtaking blue water when rain filled the abandoned quarries.

Mattietti is quick to point out that several underground sites can be accessed by curious travelers, provided they know where to look. Each summer, she guides students through lesser-known museums, such as the Crypta Balbi, located just 40 feet beneath the busy commercial thoroughfare around Piazza Venezia. Another remarkable location is the recently opened Roman Houses of Celio, revealing a beautifully frescoed villa dating back to the third century A.D. Many ancient Christian churches also house haunting chapels beneath their main structures. The Basilica of San Clemente features a Mithraeum, a sanctuary devoted to a pagan deity popular in the first century A.D., while ancient mosaics unexpectedly greet visitors in the basements of restaurants near historic landmarks like Pompey’s Theater.

However, many of Mattietti’s favorite subterranean sites require advance planning since only select locations are accessible by special request through Rome’s Special Superintendence of Archaeology. Making these arrangements often comes with a nominal fee and a lengthy process. Following a sumptuous lunch in Trastevere, with its name meaning “across the Tiber,” Mattietti guided me to the Renaissance-era Palazzo Specchi and the Church of San Paolo alla Regola. The potential for discovery hardly seemed evident until a young custodian arrived brandishing an enormous rusty key, unlocking a hidden metal door to expose creaky stone stairs lit only by dim bulbs. We exchanged glances of anticipation—as if we stood on the brink of unveiling something truly significant. “We tend to observe cities primarily from a horizontal perspective,” Mattietti pointed out. “We discuss urban growth in spatial terms. However, viewing cities in a vertical context provides a dynamic timeline, tracing all the way back to the first communities that embraced these landscapes.”

The descents led us 25 feet down into an insula, a form of Roman apartment complex. Mattietti explained how this area along the Tiber was occupied by horse stables, shipping warehouses, and sacred groves during the first century A.D., eventually transitioning into residences for poor Romans by the second century, remaining inhabited even into the Middle Ages. Archaeologists liken the various layers present in Rome to a complex lasagna, with remnants of distinct eras piled atop one another, demonstrating also that archaeological sites often overlap. “In America, we typically demolish old structures and begin anew. In ancient Rome, repurposing was common, and buildings were constructed to endure.” Some underground areas even saw use as air-raid shelters during World War II, such as the basement of the 18th-century Villa Torlonia, where Mussolini resided from 1925 until 1943.

“Here, you can find at least nine different wall types,” she said, highlighting the various designs along with embedded terra-cotta pipes and fragments of marble, alongside areas where shrimp shells were unearthed. Such peculiar details are invaluable to scholars. As we passed a discarded overflowing rubbish bin, she remarked: “Today’s refuse is tomorrow’s archaeological site.”

Exploring the once-humble dwellings deepens our understanding of Roman society, she contended. “When we admire the ruins of ancient Rome, we often see reflections of what the emperors and elite wanted us to perceive: the Colosseum, the Forums, and other monumental edifices. But the story of this city encompasses the daily lives of the ordinary Romans—those who constituted the majority and contributed to Rome’s vibrancy.”

“Why not visit ‘the cave’ for pizza tonight?” Marco Placidi, a founding member of Sotterranei di Roma, invited when I inquired about his ongoing projects. It was an offer too enticing to turn down. In 2020, he shared, the club had opened its headquarters in the Labyrinth of Rome—a complex network of tunnels extending some 22 miles beneath Caffarella Park near the historic Appian Way. This quarry, rooted in the first century B.C., once provided tuff to form the essential Roman concrete used to construct many of the city’s most renowned architectural marvels.

As dusk fell, I wandered through picturesque trails flanked by flowers, lakes filled with ducks, and wooded areas until I spotted the mossy entrance to the quarry, where several club members, including Mattietti, sat at a table enjoying pizza, olives, and wine.

“My passion for exploring underground spaces evolved gradually,” said Placidi, who works as a safety officer at a local energy company. He recounted how a friend’s visit in the late 1990s led them through heavily restricted Roman landmarks, leaving them feeling confined. “We sought out lesser-known, lesser-controlled places for exploration—where tactile experiences were possible. This often led us to Rome’s hidden underground.” In 2000, Placidi and his colleagues founded the first speleo-archaeological club; over the years, membership grew from 50 to around 2,000, attracting enthusiasts from various corners of the world.

Securing the lease for the Labyrinth fulfilled one of Placidi’s dreams. “Negotiations in the Centro Storico involve labyrinthine bureaucracy,” he lamented. “When we work around historical sites, we face many authorities, including the Superintendency of Archaeology, the Commune of Rome, the Vatican, and the water company Acea. The quarry’s private ownership offers us a great deal of freedom.”

After the pizza meal, we descended into the labyrinthine tunnels, illuminated in part by electric lights for the initial stretch. The association has transformed many of the rough-hewn chambers into meeting rooms, including a recreated Mithraeum dubbed “La Bat Caverna,” adorned with faux Roman statues framed by ferns. Regular tours and even mountain biking excursions deep into the depths are regularly offered.

Traveling deeper into the damp maze, we encountered a metal ladder leading up to a small hole in the ceiling. During the Middle Ages, tomb raiders, convinced of hidden treasures, had dug upward beneath an early Christian catacomb, only to find bone instead. A club member named Alfonso Diaz Boj, originally from Spain, began to climb, gesturing for me to follow as Placidi steadied the ladder. Soon, I found myself crawling through the darkness, my headlamp illuminating niches filled with shards of pottery, mosaics, and, rather disturbingly, human remains, including a skull. “Treasure was always the hope,” Diaz Boj lamented. “But in the end, all they discovered were bones.”

Having previously explored the more widely recognized church-run catacombs, including St. Sebastian and St. Callixtus, I found this hands-on experience unforgettable. There, in that dark alcove, covered in grime, my imagination ignited with stories of those long gone.

“Some academics criticize associations like Sotterranei di Roma for lacking professionalism,” noted Mattietti, joining us crouched in the dust. “Yet I see the members as ‘citizen scientists’—enthusiastic individuals who gain no accolades or financial rewards for their explorations. Their passion drives them.” (One member I met had tattooed on himself the letters SPQR, an acronym for Senatus Populusque Romanus, or “The Senate and People of Rome.”) “In truth, most academic archaeologists shy away from underground work. Many lack the resources or training while fearing for their safety.”

Information about underground sites spreads within the community informally. I had heard intriguing hints about clandestine lakes located beneath the Temple of Claudius on the Caelian Hill. It sounded enigmatic, almost fictional, until I learned that the city’s other speleo-archaeological group, Roma Sotterranea, organizes visits there. The following afternoon, I set out to discover the ancient temple’s entrance, now part of the Church of Sts. John and Paul. After an aimless excursion through the ornate church, a kind sacristan guided me to a hidden metal grille in a courtyard, where a group of eager visitors stood ready with hard hats.

Originally constructed following Emperor Claudius’ death in A.D. 54, the temple was once one of Rome’s grandest pagan edifices, with foundations extending 600 by 650 feet—equivalent to more than two American football fields. Our youthful guide, Chiara Massimiani, pointed out several of the magnificent temple’s intact columns still embedded within the church, leading us downstairs through metal steps into unrefined openings. Suddenly, the oppressive summer heat gave way to the subterranean, clammy air of attentively crafted tunnels mined for tuff. Within, we found a cavern housing a pair of small lakes filled with striking, crystal-clear blue waters, noted by Massimiani to be biologically pure, as rainwater had trickled through ten meters of stone above, purifying it to a level suitable for drinking. “It’s awe-inspiring to uncover such beauty a stone’s throw from the Colosseum and the Forum,” she proclaimed.

While the lakes are enchanting, the true fervor of scholars and romantics alike often resides in Rome’s engineered water systems. Prior to my journey, I managed to obtain a copy of Thomas Ashby’s seminal The Aqueducts of Ancient Rome, a work so rare it required supervision while I explored it at the New York Public Library—leafing through its brittle, yellowed pages, intricate maps, and murky images. Ashby’s sense of discovery resonates today; understanding the aqueducts is crucial to comprehending Rome’s complex history. As Mattietti pointed out, “Water didn’t just appear in the ancient city. For centuries, it was carried from the Tiber, with cisterns constructing reservoirs across the seven hills to capture rainwater. Roman engineers innovated the aqueducts to meet growing demands, transforming Rome into a metropolitan hub, allowing its population to soar to approximately one million in the first century A.D.

In my exploration of the aqueducts, I commenced at Rome’s water-themed lodging, the Anantara Palazzo Naiadi. Designed in the elaborate neo-Classical style during the late 19th century, it stands upon the dimensions of the Baths of Diocletian, an immense bathing complex from the third century A.D. accommodating 3,000 individuals at once. The hotel features mosaics from the baths in its basement alongside a rooftop pool and overlooks the Fountain of the Naiads, which features playful water nymphs and was established in 1888 alongside the revitalization of the Aqua Marcia aqueduct.

In tune with its watery legacy, the hotel hosts an early-morning jog through the original aqueduct routes, coordinated by art historian Isabella Calidonna—an activity she calls “archaeo-running.” Our route traced the daily ancient aqueduct, the Aqua Virgo, named by Marcus Agrippa, son-in-law of Emperor Augustus, back in 19 B.C. While the other ten aqueducts suffered damage from the Goths in 537 A.D., the Virgo’s underground pathways remained functional. Its decline into disuse during the Middle Ages led to a sharp population decrease in Rome, rendering it nearly a ghost town. The aqueduct was restored by Pope Nicholas V in 1453, a turning point during the Renaissance.

“Historically, water has represented power in Rome,” Calidonna noted as we set off early at 7 a.m. “In ancient times, emperors ensured public baths, and during the Renaissance, the popes commissioned breathtaking fountains.” An emblematic stop was the stunning Trevi Fountain, an 18th-century Baroque gem adorned with Oceanus, depicted in a shell-shaped chariot and surrounded by mermen. It is supported by the very Aqua Virgo, feeding into its depths. Nearby stretches of the aqueduct are perceptible; we jogged past an old section visible behind wrought iron fencing on Via del Nazareno, eventually finding ourselves in a store called La Rinascente on Via del Tritone, where a segment promised the waterway in its basement. To our surprise, the escalator delivered us to a vast expanse featuring 15 arches from the Aqua Virgo stretching nearly 200 feet. Nearby, the quirky Vicus Caprarius museum reveals the aqueduct’s remnants found during a cinema project excavation between 1999 and 2001.

Whispers about the Aqua Virgo circulate often, and rumors had reached my ears of a rarely-accessed entry point through which visitors could descend a beautiful Renaissance staircase and wade through its still-flowing waters. Gaining such access required approval from the modern water authority, Acea, akin to penetrating the Vatican. I had submitted a request two months prior, but received no response—seemingly an elusive dream.

Instead, I turned to the passion-fueled adventurers of Sotterranei di Roma, who might have insight into another captivating site. This led me to a trip back into the Roman Campagna to engage in a modest act of “guerrilla archaeology.” Placidi and Diaz Boj aimed to guide me into an ancient site that astounded Thomas Ashby just outside Vicovaro, about 30 miles from the Forum, where two aqueducts—the Claudia and the Marcia—converge. They warned me that access might be problematic as the Monastery of San Cosimato had recently closed its main entrance for repairs. “We might encounter legal trouble,” Diaz Boj joked, “but we can try!”

After our obligatory espresso stop, we parked along a quiet roadside and ventured through dense underbrush towards the tranquil Anio River. “Ecco qui!” Placidi called out, pointing excitedly at the shadowy opening before us. “Pliny the Elder claimed the Aqua Marcia had the best water in all of Rome!” Constructed between 144 and 140 B.C. under the oversight of Quintus Marcius Rex, a distant ancestor of Julius Caesar, the Marcia was the lengthiest at nearly 57 miles, feeding the source springs to Rome.

With headlamps aglow, we entered a well-preserved specus, its smooth floor and walls starkly contrasting with the rough-hewn ceiling. Diaz Boj pointed out the earlier signatures of explorers who had trekked through these corridors in the 1400s and 1600s. Moments later, he illuminated carvings made by Ashby himself, who had evidently spent a couple of nights beneath this monumental structure, leaving his mark twice.

Just days after returning to New York, I received an unexpected email from Acea, granting me permission to join an engineer in an exclusive entry to the Aqua Virgo through a restricted access point in the city’s core, featuring the storied 16th-century Villa Medici staircase. This prospect felt almost like a scene from the Da Vinci Code, compelling me to book a return flight to Rome and settle into the opulent Hotel Mediterraneo, bursting with marble-clad Roman statuary that embodied the timeless charm of history.

The following morning, I climbed to the fortress-like Villa Medici, where a discreet metal door awaited, its presence softened by a deteriorating plaque announcing the Aqua Virgo access point. Awaiting me were Marco Tesol and a small team of Acea workers, each donned in fishermen’s waders that reached our armpits, ready to descend one final time into the depths below.

Here, I would stand at the intersection of two millennia of Roman heritage. My first step was onto a spiral staircase known as La Chiocciola del Pincio—named for its snail-like shape—descending elegantly approximately 80 feet beneath the street. Previously off-limits to explorers, this Renaissance marvel boasts an extraordinary symmetry reminiscent of designs attributed to Michelangelo, constructed in 1574 by Cardinal Giovanni Ricci da Montepulciano. We took turns gingerly descending 117 weathered steps until we were enveloped by the 2,000-year-old carved tunnel of the Aqua Virgo, its clear waters gently flowing below. The aqueduct continued to operate as it had since its inauguration in 19 B.C., creating an extraordinary connection with history.

As Tesol elaborated on the aqueduct’s name, I felt a spiritually stirring camaraderie with what lay behind me. “There are two tales of the Aqua Virgo,” he explained. “One posits it symbolizes purity through its water, and another relates to the maiden who guided weary soldiers to the springs. Yet today, it’s no longer pristine for drinking.”

There was something profoundly spiritual about submerging within its waters, which had originated from distant hills and enveloped me to the waist in a cold embrace. The ground beneath us was gravelly, portions of the aqueduct had calcified, and delicate white stalactites dangled from the ceiling, showcasing the exceptional engineering that has endured through the ages. With life bubbling within the stone channels, we waded approximately 100 yards toward the Trevi Fountain. In light of its popularity among tourists, proposals had emerged for ticketing to manage the crowds effectively. We later found our way back beneath the Villa Medici and its grand gardens, tracing the paths where I had once attended enchanting events hosted by the French Academy.

As we traversed the aqueduct, we admired its architectural details, including sculpted arches and a towering 75-foot shaft intended for construction access. In a fascinating turn, Tesol noted that portions of the Aqua Virgo remained intact precisely because they lay too deep for the Goths to reach—allowing for the Renaissance restoration that kept it vital into the present day. The sixth-century chronicler Procopius detailed the Goth scouts’ earlier attempts to navigate through the Aqua Virgo, met by Roman defenders securing passageways.

After approximately 90 minutes, we emerged from the waterway and climbed back up the “Snail.” According to historians, this Renaissance staircase served another purpose besides worker access; constructed by Agrippa, it initially supported an ingenious hydraulic mechanism used to pump aqueduct waters back into the gardens. Though long since dismantled, the innovative device would remain unparalleled until modern engineers began updating Rome’s waterworks in the late 1800s, bridging the connection between ancient achievements and contemporary techniques.

Emerging from the depths, I felt exhilarated by my journey through time. Yet I reflected that perhaps I had traversed enough of il oblio for one expedition. It was time to resurface, indulging in a leisurely pasta lunch beneath the glorious Roman sun.

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