Archaeologists map underground aqueduct to the Villa of the Casoni outside Rome

Archaeologists have now pinpointed and charted the subterranean aqueduct that formerly delivered water to the Villa of the Casoni on the outskirts of Rome.

This identification resolves a puzzle first posed in the eighteenth century and indicates a water system that was already in place before Roman authority fully remodelled the wider area.

Tracing the lost aqueduct

Under the stepped, terraced remains of the Villa of the Casoni near Montopoli di Sabina in central Italy, an underground conduit runs from springs on the hillside down towards the estate.

By following cut stone faces and natural access points, Dr Nadia Fagiani of the regional archaeological authority was able to show precisely where the channel entered the villa’s internal waterworks.

Rock-hewn tunnels together with an attached cistern indicate that water once moved through one continuous, connected system, rather than as disconnected remnants described for years in older writings.

With the layout confirmed on the ground, those earlier reports can now be fixed to a mapped structure, making it possible to investigate how the remainder of the network operated.

Reading the old notes

Towards the end of the 1700s, local scholars wrote about very ancient signs of an aqueduct and a spring that later became known as Fonte Varrone.

Writers in the 1800s repeated the same idea, but no-one was able to match the descriptions to a plotted course.

Detailed topographic analysis and systematic field survey work have now linked those notes to specific tunnels, springs, and a buried intake.

Establishing that physical connection also tightens the search area for earlier settlements that may have been responsible for the original construction.

Inside the tunnel network

At a distance of about 300 metres (980 feet) from the villa, investigators reached an underground network that splits into branches and still tracks the descending slope.

These corridors are known to archaeologists as cuniculi-slim, hand-cut tunnels created to carry water through solid rock.

Cut straight into the bedrock, the channels collected water from multiple springs and channelled it into a single gathering chamber.

Because the passages are so narrow, they would have required regular maintenance: a blocked shaft or a collapse could halt the supply well before it arrived where people needed it.

Cleaning water before use

Before the springwater was put to use, it was routed into a cistern where a slower current allowed suspended matter to settle out.

At this point the builders formed a piscina limaria, a settling tank designed so sand and silt would sink.

Once the sediment had dropped, clearer water returned to the tunnels and supplied the villa’s fountains and baths.

Even this straightforward filtration could be overwhelmed at times, as seasonal floods might still muddy the flow, meaning intake points needed safeguarding.

Water shaped the villa

The estate was arranged around two descending terraces, with an ornamental garden on the lower level and more private accommodation above.

A dependable water supply enabled the owners to keep a circular pool clean and to sustain shaded paths during the hottest part of the summer.

On the lower terrace, a nymphaeum-a grotto-like garden sanctuary associated with water-served as a focal feature next to the pool.

Long before municipal pipes, that consistent supply helped make the hillside property a setting for welcoming guests rather than simply an agricultural holding.

Clues before Roman rule

Building techniques point to the water system having begun before Roman power fully influenced this part of the Sabina region.

Rather than one uniform, finely finished channel, the works combine water capture with drainage, a configuration often seen in earlier countryside engineering.

It is possible that local organisers established a vicus, a small rural settlement linked to farms, and that later construction adapted those earlier water lines to serve the villa.

Establishing when the first excavation occurred will rely on sediments and finds sealed in undisturbed layers, because masonry by itself rarely provides firm dates.

Scanning tunnels in 3D

To align the concealed waterways with the visible remains above ground, the team intends to undertake a full three-dimensional survey within the tunnels.

By using LiDAR-laser scanning that records distances in 3D-they can document the walls without physically contacting them.

“LiDAR will make it possible to obtain a complete 3D map of the entire underground hydraulic system, linked precisely to the villa’s walls and rooms,” said Fagiani.

More accurate mapping should also cut down on uncertainty, supporting the protection of delicate passages and guiding decisions about where careful excavation might still be carried out safely.

Collaboration below ground

Speleologists negotiated low, cramped corridors, recorded bearings, and photographed sections that surface work could not reach safely.

In cooperation with state heritage personnel, Italy’s Vespertilio Speleo-Archaeological Group contributed rope-access methods and specialist underground safety skills to the project.

Input from local landowners proved important as well: they recalled an old trough once supplied by the springs and directed the teams further downhill.

Investigations of this kind tend to progress more quickly and with fewer risks when archaeologists, cavers, and residents share responsibility at every stage.

Water in the Sabina hills

Beyond the story of a single estate, the tunnels illustrate how hillside communities managed water long before Rome imposed standard approaches across the countryside.

Researchers from the University of Basel have combined on-the-ground survey work with environmental analysis to reconstruct land use around the villa.

From its ridge to the north-east of Rome, the site overlooks the Tiber Valley and the River Farfa, an important watercourse locally.

Connecting the newly mapped aqueduct to evidence from soils and cultivation could show whether controlling water helped sustain productivity in the region over many centuries.

Future excavation plans

Material from the tunnels, the springs, and the settling tank now firmly links the villa to a supply system that had been described for generations but never previously located.

Future dating work, comprehensive 3D mapping, and carefully managed access will determine how much of the network can be examined in detail-or potentially opened to visitors.

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