Luke Irwin, a British rug designer, said he had hired workmen to lay underground electricity cables to an old barn on his property in Brixton Deverill, about 20 miles southeast of the former Roman spa town of Bath, last year.
About 18 inches below the topsoil, they struck a hard surface of orange, cream and grey mosaic tiles.
Realizing the likely significance of a mosaic beneath the ground in a remote field, Irwin told the workmen to stop what they were doing, and called in archaeologists instead.
"To actually find something like that is absolutely extraordinary," he told CNN. "You're kind of overwhelmed by it, to be honest."
A team of archaeologists subsequently carried out a 10-day exploratory dig, excavating eight trenches on the property. They found that Irwin's farmhouse lay on the site of an impressive Roman villa, thought to be one of the largest in the country, built between 175 A.D. and 220 A.D., and remodeled until the mid-fourth century A.D.
"Without question, this is a hugely valuable site in terms of research, with incredible potential," David Roberts, leader of the excavation and an archaeologist for the government's Historic England service, said in a statement.
A 'family making their mark'
He said the ancient property, which would have been visible from a nearby Roman road, was "not a subtle country house," but the "showy" property of a "family making their mark."
"The discovery of such an elaborate and extraordinarily well-preserved villa, undamaged by agriculture for over 1,500 years, is unparalleled in recent years. Overall, the excellent preservation, large scale and complexity of this site present a unique opportunity to understand Roman and post-Roman Britain. "
It is believed the three-story villa, with a footprint of at least 50 meters by 50 meters (nearly 55 yards by 55 yards), would have belonged to a wealthy and powerful family. Archaeologists have compared it in scale and significance to Chedworth, a Roman villa
discovered in 1864.
Other artifacts found nearby included a bath house, well, pottery and coins, and discarded oyster shells that the ancient inhabitants would have dined on.
Researchers also determined that a stone planter near Irwin's kitchen that had been used to house geraniums was actually originally the coffin of a Roman child.
Irwin said the plan for the site was not yet clear, but he hoped it would be given the proper excavation it deserved.