A buried Roman racetrack 450 meters long, discovered using ground-penetrating radar without moving a shovel of dirt. Modern geophysics revealed the chariot track's starting gates, spine, and seating for 20,000 spectators - all hidden underground.
Finoskov, CC BY-SA 3.0
Imaging the invisible
Beneath a quiet patch of ground on the bank of the Rhône, the full scale of the Roman Circus of Arelate lies mapped in precise detail. No large-scale excavation was needed to reveal it. Instead, geophysical survey techniques produced a complete image of the buried structure. Using a combination of ground-penetrating radar and magnetic gradiometry, archaeologists created a high-resolution plan of the racetrack, which was built in 149 AD.
The resulting data shows the circus's classic layout. The plan reveals a 450-meter-long and 101-meter-wide arena capable of holding 20,000 spectators. Also visible are the carceres—the twelve starting gates for the chariots. The long central barrier, or spina, around which the chariots raced, appears clearly in the geophysical data. This barrier was once decorated with sculptures, basins, and a tall granite obelisk that now stands in Arles' Place de la République. The rounded end of the track, the sphendone, is also perfectly delineated. This non-invasive approach allowed for a complete study of the largest Roman monument in Arles without disturbing the ground above it.
Imperial engineering and decline
The construction of the Arles Roman Circus was an immense engineering challenge. Built on the unstable, clay-rich banks of the Rhône, its foundations required 30,000 wooden piles, each two to three-and-a-half meters long, to be driven into the ground to provide stability. The main structure was used primarily for chariot and horse races, but also for cavalry battles and staged animal hunts called venationes. The track itself was wide enough for twelve chariots to compete simultaneously.
The circus saw continuous use for centuries, undergoing a major renovation in the 4th century when the spina was updated with marble veneers and the obelisk was installed. By the 5th century, small dwellings began to appear around and even inside the structure's arches, though races were still being held. Its end came in the mid-6th century when the monument was systematically dismantled. Its stones were repurposed to reinforce the city walls against threats. After its abandonment, frequent flooding from the Rhône buried the remaining foundations under layers of alluvial silt, hiding it from view for centuries. Today, the only physically visible remains are parts of the substructure of the seating area, located beneath the modern Musée départemental Arles antique.
💡Fun Facts
The circus was built on marshy ground requiring a massive foundation of 30,000 wooden stakes to stabilize the structure.
The central granite obelisk that decorated the circus's spine was rediscovered in the 14th century and erected in the city's main square in the 17th century, where it still stands.
After the circus fell into disuse, its stones were systematically removed in the 6th century to strengthen the city's defensive walls.
Repeated flooding from the nearby Rhône river buried the ruins in silt, which is why it remained hidden until modern archaeological methods revealed it.
The ground above the buried circus is publicly accessible. For artifacts and a model of the circus, visit the Musée départemental Arles antique, open 9:30 AM - 6:00 PM; closed on Tuesdays.
Admission
Free to walk over the site. Museum admission is €8.
Accessibility
The ground above the circus is generally flat. The adjacent museum is accessible for self-propelled wheelchairs.
