Archaeologists, who were left stunned by the degree of preservation, have said the only reason they survived was because Priory Park was never built on.

Two houses and a third building were found. Moving images from a scan show the shapes of two buildings emerge.

It is thought the houses in Noviomagus Reginorum - the Roman name for the town - were owned by people of importance.

Local geophysics specialist David Staveley, who had set out to identify all the city's Roman roads, was given permission to scan the parks because some might have survived there.

Following his scans, a small dig was carried out in Priory Park.

It is thought the houses were originally on a street but the road did not survive.

James Kenny, an archaeologist at Chichester District Council, said the scans showed a townhouse with rooms and a freestanding building in the corner.

"It's difficult to say what it might have been, but the walls did survive. It might have been part of a bathhouse, or a cellar, or a winter dining room with under-floor heating," he said.

Mr Kenny admitted there was "nothing exceptional" about a Roman house in a Roman town.

But he said: "What's exceptional is in a Roman town like Chichester, most of the archaeology has been interrupted by all sorts of house building."

Added to that, the city had no sewers until the 1880s and people had to dig holes in the ground, he said.

"An awful lot of archaeology was lost."

However, Priory Park, originally home to a monastery, had not been developed, and the buildings buried 0.5m below the surface showed a "remarkable degree of preservation", Mr Kenny said.

Further exploration will take place this year and there may also be a larger investigation in the future.

Scans also revealed another Roman street under the park, but this will not be uncovered.