Beneath the cobblestones of Rome, under its ancient basilicas, bustling piazzas, and tourist-lined avenues, lies a vast and mostly forgotten world—one that continues to astonish archaeologists, locals, and explorers alike. Among its hidden marvels are the famed Roman aqueducts, ancient Christian catacombs, and even mysterious sites like the Grottino del Campidoglio, or Capitoline Grotto, a shadowy and little-documented chamber said to lie under the Capitoline Hill, where ancient Romans may have believed the underworld touched the city above.
So why is so much of this ancient world underground? Much of imperial Rome is, quite literally, buried beneath itself. Over the centuries, layers of construction, collapse, and rebuilding—especially since the fall of the Western Roman Empire in A.D. 476—have raised the city’s surface by nearly 30 feet in some places. “Many people think of imperial Rome as a lost city,” said Giuseppina Mattietti, an earth scientist at George Mason University, “but that’s the interesting thing: It’s not gone! Romans just built on top of it, for century after century” (Smithsonian, April/May 2025).
How do explorers today uncover this buried treasure? In part, it’s thanks to citizen scientists—modern “speleologists,” or cave archaeologists—who crawl, climb, and sometimes even swim their way through the hidden passages beneath Rome. Groups like Sotterranei di Roma, or the Undergrounds of Rome, take this mission seriously, often venturing into long-forgotten aqueducts and maintenance shafts, many of which have been dry or unused for over 1,500 years.
In one such expedition, Luca Messina, a civil engineer and speleo-archaeologist, led a team into a segment of the ancient Aqua Anio Vetus, a marvel of Roman engineering built in 272 B.C. that had lain dormant for centuries. “Don’t worry about those insects,” he told a reporter, pointing to walls hewn over 2,300 years ago and crawling with spider-like Dolichopoda crickets. “They aren’t dangerous” (Smithsonian).
Much of the search today relies on retracing the steps of famed archaeologist Thomas Ashby, who, between 1906 and 1925, produced the most detailed early maps of Rome’s aqueduct system. Yet his descriptions often rely on landmarks that no longer exist. “Ashby mapped many aqueducts in detail, but he obviously had no GPS and couldn’t cite precise locations,” Messina explained. “We try to identify the spots he found a century ago, map them with GPS systems and post them on Google Earth” (Smithsonian).
Among the most fascinating sites are those where ancient engineering and Christian tradition intersect. Many churches in Rome sit atop earlier pagan temples or baths, and below their altars lie the remains of Roman homes, shrines, and catacombs. At the Basilica of San Clemente, for instance, one can descend through layers of Christian, pagan, and imperial Roman structures—eventually reaching a Mithraeum, a shrine to a mysterious Eastern cult that rivaled early Christianity.
Even beyond the church-managed catacombs, explorers have found cemeteries long forgotten. In one excursion, members of Sotterranei di Roma crawled through the tunnels beneath the Labyrinth of Rome, a 22-mile network of passages under Caffarella Park. “All they found were bones,” one member noted after climbing through a hole once dug by medieval tomb raiders hoping for treasure. Instead, they encountered Roman mosaics and human remains (Smithsonian).
What does this mean for Catholics today? For one, it reminds us that Rome’s history is not just the story of emperors and palaces—it is a story of the Church and its endurance, buried in the very ground we walk on. The Christian catacombs remind us of the martyrs. The aqueducts, painstakingly restored during the Renaissance, echo the ingenuity and perseverance of generations who refused to let the city die. And even the grotesque beauty of stalactites in the Aqua Virgo tunnel calls to mind the humility of water—simple, essential, and life-giving.
In the Renaissance-era Villa Medici, modern water engineers still descend a spiral staircase known as La Chiocciola del Pincio into the still-flowing Aqua Virgo—Rome’s only ancient aqueduct that continues to function today. Built in 19 B.C. by Marcus Agrippa, it feeds the Trevi Fountain, the world-famous Baroque marvel where pilgrims and tourists alike cast coins in hope. “Most of the Vergine was too deep for the Goths to destroy,” explained Marco Tesol, an engineer with Rome’s water board. “That’s why it could be restored in the Renaissance and flows today” (Smithsonian).
The presence of Christian relics and sacred spaces underground also calls to mind the Church’s deeper theological message: that beneath the surface of this world lies a spiritual reality that often goes unseen. As we walk the streets of Rome—or of any city built on a Christian foundation—we are reminded that the Church was built not by the powerful, but by those hidden from view: the faithful, the martyrs, the workers, and the saints.
Rome’s underworld, in all its dusty, damp, and silent mystery, is not just a playground for archaeologists or a curiosity for tourists. It is a mirror of Christian memory—layered, luminous, and waiting to be uncovered.
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