Thanks to new technology, archaeologists are getting their first glimpse into life in Old Sarum, a once-thriving medieval city not far from Stonehenge, and the ruins hidden beneath include what may have been one of the largest palaces of the period.

Located near the modern city of Salisbury, the English Heritage site resembles two raised grassy rings, with the inner ring once home to a castle.

A few stone walls and some ruins are all that remain. But by using techniques such as ground-penetrating radar, researchers from the University of Southampton have found a series of massive structures in the outer ring, or bailey, that may have been part of the city's defenses, as well as a number of homes from the settlement's heyday some 700 to 900 years ago.

“Archaeologists and historians have known for centuries that there was a medieval city at Old Sarum, but until now there has been no proper plan of the site," Kristian Strutt, experimental officer and director of archaeological prospection services at the University of Southampton, said in a news release. “Our survey shows where individual buildings are located and from this we can piece together a detailed picture of the urban plan within the city walls."

The scans also turned up a large open area, more than 550 feet long, which one expert believes may have been part of a royal complex.

“The location, design and size of the courtyarded complex strongly suggests that it was a palace, probably a royal one," Dr. Edward Impey, director-general of the Royal Armouries and a leading expert on high status medieval buildings told the Independent. "The prime candidate for constructing it is perhaps Henry I sometime in the early 12th century.”

In addition, the research team found kilns or furnaces and evidence of quarrying that took place after the city had fallen out of favor.

Along with radar, the researchers used magnetometry, earth resistance and electric resistivity tomography to discover what sits beneath the bailey.

"The plan shows for the first time just how much other activity there was around the castle and cathedral which have long been known," Neil Holbrook from Cotswold Archaeology told the BBC. "It sets those monuments within the context of a bustling, vibrant town established shortly after the Norman conquest."

Old Sarum's history goes back some 5,000 years. By 400 BC, during the Iron Age, a fort had been built on the site. Later, it was occupied by the Romans.

The castle was built in the 11th century, and some believe it may have been a place for nobles to come and pledge allegiance to the conquerers.

"This castle wouldn’t have just dominated the site of Old Sarum itself, but the surrounding countryside as well," aerial archaeologist Ben Robinson said when describing the site on a recent episode of iTV's "Secrets From The Sky."

A cathedral was built in Old Sarum in 1092. But the city's decline began in the 13th century, when a new cathedral was constructed in what is now the modern city of Salisbury, according to background information provided by the University of Southampton. Salisbury Cathedral remains in operation today.