What archaeological mysteries are still buried beneath the streets of Rome?

Ancient legend often blend into archaeology when it comes to Rome’s founding heroes.

A dramatic example is the recent discovery of what may be the Tomb of Romulus, Rome’s mythical first king.

In 2020, archaeologists announced they had found a stone sarcophagus and circular altar buried beneath the Forum, right next to the Black Stone (Lapis Niger) shrine where Romans believed Romulus was slain.

The entrance to this underground chamber was hidden under the steps of the Curia (Senate House) in the northwest Forum.

Inside, a 1.4 m tuff sarcophagus lay empty beside the altar. Ancient authors like Varro mentioned Romulus’s tomb in this vicinity, but scholars debate whether Romulus ever existed.

At the very least, this find confirms that Romans of the Republic venerated a founder’s tomb here.

The site has been documented with 3D laser scans and is slated for further excavation.

Equally evocative is the Lupercal cave, the sacred grotto where legend says a she-wolf suckled the twins Romulus and Remus.

For centuries the Lupercal’s location was unknown. But in 2007, Italian archaeologists using endoscopes and laser scanners found a vaulted cavity 16 metres inside the Palatine Hill near Emperor Augustus’s palace.

The chamber is richly decorated with seashell mosaics and marble, and an eagle emblem on its ceiling, all consistent with ancient descriptions of the Lupercale sanctuary, which Augustus himself restored.

Experts are highly confident this is the long-lost Lupercal. However, it remains buried and inaccessible: worried that a full dig could collapse it, archaeologists have so far peered in only with probes.

Plans were debated to either excavate an entrance from the hillside or enlarge the probe hole from above.

The Lupercal’s exact orientation and any artifacts inside are still mysterious. This find shows how even Rome’s mythic sites lie waiting underground, in this case, protected for 2,000+ years until technology allowed its rediscovery. 

Dozens of temples that once graced Rome have vanished from sight, but not necessarily destroyed.

Many lie in ruins under busy streets or buildings, known only through records or chance finds.

For example, the Temple of Diana on the Aventine Hill, said to have been founded in the 6th century BC by King Servius Tullius, has left barely a trace.

Ancient writers celebrated it as a grand sanctuary of the Latin League, yet today only scant remains are visible and much of it likely lurks under later structures.

Archaeologists speculate that foundations of Diana’s temple, and perhaps ritual deposits, could be preserved beneath the Aventine’s parks or churches, awaiting exploration. 

Likewise, on the Quirinal Hill, remnants of a colossal temple dedicated to Serapis (an Egyptian-Hellenistic deity) hint at what lies below.

Erected in the 3rd century AD (probably by Caracalla or Aurelian), this Temple of Serapis was one of the largest in Rome.

It was demolished in late antiquity and its stone repurposed, but huge fragments survive, including a 100-ton marble capital, in the Colonna palace gardens.

These suggest a massive podium and column shafts still underground. Given its scale, archaeologists are excited by the prospect of tunnelling or ground-penetrating radar to map the temple’s footprint beneath the modern hilltop.

So far, only small portions have been examined, but any future excavation here could reveal one of ancient Rome’s most monumental religious sites. 

Even in the city centre, temples hide in plain sight. In the Largo Argentina square, for instance, four Republican-era temples were unearthed in the 20th century.

Yet around them lie hints of other structures, possibly the lost temples of Virtus and Fortuna from Sulla’s time, that remain unexcavated under nearby streets.

Each new construction project in Rome has the potential to expose another “lost” temple.

It’s telling that when plans for a Metro station at Largo Argentina were proposed, archaeologists had to halt work because every test shaft struck ancient remains.

The city is so dense with antiquities that whole sanctuaries can lurk undisturbed beneath cafés and shops. 

While famous emperors’ tombs like the Mausoleum of Augustus are above ground, others are missing or only recently found.

We’ve seen how Romulus’s supposed tomb came to light under the Forum.

Another longstanding mystery was the Tomb of Nero, the resting place of the notorious emperor (d. 68 AD) who was denied burial in Augustus’s mausoleum.

Ancient accounts say Nero’s ashes were placed in the tomb of his paternal family (the Domitii) on the Pincian Hill, just outside the old city wall.

This grand sepulchre was visible for centuries. By around 1099 AD, however, it had gained a negative reputation, as medieval legend claimed Nero’s malevolent spirit, in the form of crows, haunted the spot.

Pope Paschal II responded by demolishing the tomb and building a chapel, later replaced by the Church of Santa Maria del Popolo. 

Is anything left of Nero’s tomb today? In fact, yes. In the 20th century, an underground chamber was found beneath the adjacent monastery, cut into the Pincian Hill’s slope.

Archaeologists believe this hidden vault is the last remnant of the Domitii Mausoleum, likely Nero’s own burial chamber.

The above-ground monument is gone, but its foundation and possibly some funerary niches endure, sealed off beneath church property.

It’s a fascinating case of a “vanished” imperial tomb that, in part, still exists out of sight.

With permission to excavate further (a delicate issue on consecrated ground), scholars hope to confirm the identification, perhaps even find traces of inscriptions or offerings that escaped medieval destruction.

Nero’s tomb is not the only one: many ill-fated or obscure figures’ graves remain untraced.

The final resting places of various 3rd–5th century emperors, usurpers and saints around Rome are often known only from texts.

Some were likely robbed out or destroyed, but others could lie beneath later cemeteries or churches, waiting for a chance discovery. 

Another intriguing example is the Mausoleum of Romulus, not the founder king this time, but the young son of Emperor Maxentius.

This circular tomb from the early 4th century sits along the Appian Way (just outside the city) and was long thought to be empty.

In 2021, however, archaeologists unexpectedly found intact remains of elaborately carved sarcophagi inside it, showing that even “known” tombs can hold surprises once fully explored.

Beneath Rome’s busy thoroughfares lies a labyrinth of tunnels, some engineered by the ancients, others natural or accidental.

Perhaps the most legendary is the Cloaca Maxima, the Great Sewer of Rome. First built in the 6th century BC (traditionally by King Tarquin), this arched drain is one of the world’s oldest still-functioning sewers.

It carried waste and storm water from the Forum to the Tiber, and remarkably parts of it still flow today, hidden below the Forum and downtown streets.

Intrepid “urban speleologists” have donned hazmat suits to explore the Cloaca’s fetid tunnels, even wading through waist-high water under the Forum.

Much of its course is unmapped, a risky undertaking since sections occasionally cave in, causing sinkholes that swallow modern cars!

(In fact, Rome has been dubbed the “sinkhole capital of Europe” due to this phenomenon.)

Archaeologists hope to properly map these ancient sewers with modern equipment, as they may hide small artifacts or branch into forgotten cisterns.

The Cloaca Maxima itself was considered such a marvel that ancient writers like Pliny the Elder raved about its construction. 

The city also harbours miles of catacombs, networks of burial galleries used by Jews and Christians in the 2nd–4th centuries AD.

Over 60 catacomb complexes are known, with more than 150 kilometres of tunnels twisting beneath the outskirts of Rome.

New catacomb sections are occasionally found by accident (for example, during building works or when sinkholes open).

It is very plausible that undiscovered catacombs or crypts still lie under areas that were once outside the ancient walls.

Similarly, pagan Rome’s underground cult sites pop up in surprising places. In 1931, for instance, workers under the Circus Maximus racetrack found a secret Mithraeum (temple of the god Mithras) 13 metres down, complete with frescoes and altars, showing how a shrine could be hidden right below a major public venue.

Countless service tunnels and vaults also exist under imperial buildings. The Colosseum’s substructure (hypogeum), a two-level warren of galleries for gladiators and animals, is now open to visitors, but only recently have restorers noted ancient graffiti preserved on its walls.

And under some modern buildings, Roman passages survive: e.g. beneath a luxury hotel near the Forum, archaeologists have opened a 2,000-year-old drain and storage tunnel as an exhibit.

These subterranean spaces, whether originally for water, burials, or backstage use, form a giant jigsaw puzzle under the city.

Explorers today describe the underground of Rome as a “honeycomb” of hidden features.

Aside from sewers and catacombs, there are cisterns and quarry caves (some later converted to clandestine medieval worship sites or even World War II bomb shelters).

On the Caelian Hill, an ancient tuff quarry was abandoned and later filled with water, creating crystal-blue underground lakes that still exist in the dark beneath a 12th-century church.

On the Palatine, archaeologists have crawled through narrow cryptoporticus corridors that once connected imperial palaces, some so untouched that soot from ancient torches still blackens the ceilings.

Even Rome’s most famous ancient structures have “missing pieces” that could be found in the future.

Take the Colosseum: while its above-ground ruins are iconic, archaeologists suspect there may be undisturbed sections of its foundations or nearby outbuildings underground.

In fact, during Metro excavations a few years ago, workers came across traces of machinery and equipment used to build the Colosseum, possibly an ancient workshop or crane base, which had been buried for 1,900 years.

Similarly, the Forum of Trajan is only partially exposed; a large portion of this imperial forum (including Trajan’s temple and libraries) lies under a later city quarter.

Plans are afoot to excavate more as traffic is re-routed. Already, creating the new Via dei Fori Imperiali road in the 1930s sliced through these remains, and recent projects have recovered sculptures and columns from the fill.

One extraordinary example of literally missing pieces turning up is the Domus Aurea, Emperor Nero’s sprawling Golden House.

This palace was built in the aftermath of the great fire of AD 64, and it was so huge that it covered parts of four of Rome’s seven hills.

After Nero’s death, the Golden House’s rooms were back-filled with earth and built over (the Colosseum, in fact, was built atop Nero’s drained artificial lake).

Fast-forward to modern times: Renaissance explorers rediscovered some painted halls in the 15th century, and many rooms have since been excavated and restored.

Yet new chambers continue to be found unexpectedly. In 2019, restorers setting up scaffolding struck a hollow area, revealing the “Sphinx Room,” a hidden vault adorned with vivid frescoes of centaurs, panthers, and a sphinx.

Its curved ceiling, 4.5 m high, had preserved bright red, green and yellow murals for nearly 2,000 years.

Archaeologists estimate this room dates to Nero’s reign (c. 65–68 AD) and had been entombed when later emperors built baths over the palace.

Much of the Sphinx Room is still filled with soil, it has literally been buried all this time, so only the upper decoration is visible for now.

Plans are underway to carefully excavate it in the future. The Domus Aurea, by one count, had at least 300 rooms , and many have yet to be uncovered.

Likewise, other imperial residences on the Palatine likely conceal unopened rooms sealed by later collapses.

Archaeologists are using techniques like micro-cameras inserted through crevices, and ground-penetrating radar scans of mound areas, to detect hollow spaces that could be unexplored rooms. 

Even vanished monuments sometimes leave ghostly imprints underground. The Colossus of Nero, a 30-metre bronze statue that once stood beside the Colosseum, disappeared in late antiquity, likely melted down.

But in 19th-century digs, a massive brick pedestal was found, believed to be the base of this giant statue.

Though that base was removed in the 1930s construction, records and a few vestiges survive, so the exact spot of the Colossus is known.

Who knows, perhaps fragments of the bronze colossus (toes? a sun-ray crown?) might still lie in a yet-unexplored drain or foundation nearby.

Another case is the Circus of Nero in what is now Vatican City. This arena, where Emperor Nero held chariot races and where St. Peter was martyred, was largely built over by Old St. Peter’s Basilica.

Yet during excavations of the Vatican Necropolis in the 20th century, archaeologists identified part of the circus’s foundations deep under the basilica.

Some of Nero’s circus is therefore literally beneath the church, and portions of its spina (central barrier) and seating may still be intact under the Vatican grounds.