Archaeologists Use Ground-Penetrating Radar to Map Ancient Roman City of Falerii Novi

The first high-resolution ground-penetrating radar survey of a complete ancient Roman town — Falerii Novi, in Lazio, Italy — has revealed previously unrecorded public buildings, such as a temple, a macellum or market building, a bath complex, and the ancient city’s network of water pipes.

Ground-penetrating radar (GPR) is a reliable method that provides high-resolution 3D images of buried structures.

It relies on the reflection of electromagnetic waves at transitions between materials of a different dielectric permittivity.

The amplitudes and travel times of the reflected waves are measured, resulting in vertical radargrams or profiles. Using several parallel radargrams, horizontal slices at different depths (‘time-slices’ or ‘depth-slices’) can be created.

By towing their GPR instruments behind a quad bike, a team of archaeologists from the University of Cambridge and Ghent University surveyed all 30.5 hectares within the walls of Falerii Novi.

The researchers collected 71.7 million readings, each consisting of 400 temporal samples, equating to 28.68 billion data points — approximately 4.5 GB of raw data per hectare.

“The astonishing level of detail which we have achieved at Falerii Novi, and the surprising features that GPR has revealed, suggest that this type of survey could transform the way archaeologists investigate urban sites, as total entities,” said Professor Martin Millett, a researcher in the Faculty of Classics at the University of Cambridge.

Located approximately 50 km to the north of Rome, Falerii Novi was founded in 241 BCE, following the destruction by Rome of the nearby Faliscan center of Falerii Veteres.

Occupation at Falerii Novi continued through Roman times and down to the early medieval period (sixth to seventh centuries CE).

The new study challenges certain assumptions about Roman urban design, showing that Falerii Novi’s layout was less standardized than many other well-studied towns, like Pompeii.

A temple, a macellum and a bath complex discovered by the team are also more architecturally elaborate than would usually be expected in a small city.

In a southern district, just within the city’s walls, GPR revealed a large rectangular building connected to a series of water pipes which lead to the aqueduct.

Remarkably, these pipes can be traced across much of Falerii Novi, running beneath its insulae (city blocks), and not just along its streets, as might normally be expected.

“This structure was an open-air natatio or pool, forming part of a substantial public bathing complex,” the scientists said.

“Even more unexpectedly, near the city’s north gate, we identified a pair of large structures facing each other within a porticus duplex (a covered passageway with central row of columns).”

“We know of no direct parallel but believe these were part of an impressive public monument, and contributed to an intriguing sacred landscape on the city’s edge.”

The results are published in the journal Antiquity.

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Lieven Verdonck et al. 2020. Ground-penetrating radar survey at Falerii Novi: a new approach to the study of Roman cities. Antiquity 94 (375): 705-723; doi: 10.15184/aqy.2020.82