Archaeologists have unearthed the remains of a roofed theatre, a market and a river port at the site of a Roman town in central Italy, challenging assumptions about the Empire’s decline.

The Cambridge University-led study suggests that Interamna Lirenas was a thriving town whose decline began around 300 years later than previously thought.

Analysis of pottery excavated at the site, which is now largely crop fields, indicated that the town in Southern Lazio resisted decline until the later part of the 3rd century AD.

At its peak, the town would have housed around 2,000 people, according to the study.

Dr Alessandro Launaro, the study’s author and Interamna Lirenas Project lead at Cambridge’s Classics Faculty, said: “We started with a site so unpromising that no one had ever tried to excavate it – that’s very rare in Italy.

“There was nothing on the surface, no visible evidence of buildings, just bits of broken pottery.

“But what we discovered wasn’t a backwater, far from it.

“We found a thriving town adapting to every challenge thrown at it for 900 years.

“We’re not saying that this town was special, it’s far more exciting than that.

“We think many other average Roman towns in Italy were just as resilient.

“It’s just that archaeologists have only recently begun to apply the right techniques and approaches to see this.”

He continued: “Based on the relative lack of imported pottery, archaeologists have assumed that Interamna Lirenas was a declining backwater.

“We now know that wasn’t the case.”

The research team conducted a series of digs and carried out a magnetic and ground-penetrating radar (GPR) survey of around 60 acres.

The survey near the River Liri revealed the presence of a large warehouse of 40 metres by 12 metres, a temple and a bath complex.

The researchers are confident that these structures served a river port between the late first century BC and the fourth century AD.

They discovered the remains of a roofed theatre along the north-western side of the town which would have towered over an open terrace.

The theatre, which boasted diverse marbles imported from across the central and eastern Mediterranean and was around 45 metres by 26 metres, could have seated 1,500 people.

Roofed theatres are quite rare in Roman Italy and represent a significant upgrade on open-air structures, acoustically, architecturally and financially.

“The fact that this town went for a roofed theatre, such a refined building, does not fit with a backwater in decline,” said Dr Launaro.

“This theatre was a major status symbol.

“It displayed the town’s wealth, power and ambition.

“The assumed lack of a theatre here was taken as evidence of the town’s early decline.

“At nearby Roman towns, archaeologists saw the remains of theatres sticking out of the ground.

“The remains of Interamna Lirenas’s amazing theatre was there all along, just completely buried.”

The team identified 19 courtyard buildings which they believe may have served as indoor market buildings, guildhouses, apartment blocks and public warehouses.

They also found a large open space, of over one acre, to the south-east of the town which they believe served as a sheep and cattle market.

The archaeologists did not find a layer of ash or any other evidence to suggest that the town was violently destroyed.

Dr Launaro argues that inhabitants probably deserted the town amid growing insecurity but before the Lombard invasion of the late sixth century AD, because they knew they were on a direct route which marauding armies were bound to use.

The team’s re-appraisal of a now-lost inscription found in the 19th century indicated that Interamna Lirenas gained the patronage of Julius Caesar in 46 BC.

Dr Launaro said the town “would have been valuable” to Caesar as it was “strategically located between a river and a major road, and it was a thriving node in the regional urban network”.

The 13-year-long study is published today in the edited volume Roman Urbanism in Italy.