The archaeological site at Trusty’s Hill in Galloway, Scotland, is known to have been a cultural center for the Pict, the confederation of tribal peoples that lived in what is now northern and eastern Scotland during Roman times. After some five years of excavation, however, researchers working there now believe they have uncovered something far more important: the site of the long-lost Dark Age kingdom of Rheged. Though the kingdom featured prominently in Arthurian legend, inspired early medieval poetry and left historical records of dominance, its location has remained a mystery for centuries.

Archaeologists began excavations at Trusty’s Hill back in 2012, after finding ancient Pictish symbols carved into an outcropping of rocks near the entrance to the site. The carvings were unique in the region, which is far to the south of where Pictish carvings had usually been found. (Roman writings of around A.D. 300 described the Picts as the hostile tribes of the region north of the Firth of Forth and the Firth of Clyde; they are thought to have been a loose confederation of Celtic tribes, but their exact origins are uncertain.)

What the archaeologists uncovered at the site turned out to be a complex type of fort, dating to around A.D. 600. A wooden and stone rampart had been built around the summit of the hill to fortify the site, in addition to other defensive structures and enclosures on its lower slopes. The style was consistent with other high-status settlements of the early medieval period in Scotland.

This was not a run-of-the-mill agricultural settlement, in other words, but a far more important center. Dr. David Bowles, a Scottish Borders Council archaeologist and co-director of the dig, believes its inhabitants likely managed the farming and natural resources of a much larger estate. As Bowles told the Independent of the settlement’s influence: “Control was maintained by bonding the people of this land and the districts beyond to the royal household, by gifts, promises of protection and the bounties of raiding and warfare.”

Just how influential was this royal settlement? According to Ronan Toolis of GUARD Archaeology, which led the dig, the archaeological evidence collected at Trusty’s Hill “suggests that Galloway may have been the heart of the lost Dark Age kingdom of Rheged, a kingdom that was in the late sixth century pre-eminent amongst the kingdoms of the north.”

Toolis, Bowles and their team believe the entranceway, with the two Pictish symbols flanking it, was the location for royal inauguration ceremonies that took place at the fort complex. They also found evidence of leatherworking and wool spinning operations at the ste, along with the remains of a metal workshop that appears to have produced high-quality work in gold, silver, iron and bronze.

Among the kingdoms of Dark Age Britain, Rheged has remained the most elusive. The kingdom and its powerful warrior king, Urien, inspired some of the earliest medieval poetry composed in Britain, by the poet Taliesin. In some Arthurian legends, Urien is said to have married Morgan Le Fay, King Arthur’s sister. Their marriage was reportedly not a happy one; in one version of events, Morgan plotted to use the sword Excalibur to kill Urien and Arthur and take the throne herself with her lover, Accolon.

Surviving fragments of early medieval historical records also show Urien’s dominance in southern Scotland and northern England, before a rival group destroyed the settlement in the early seventh century. But despite its historical importance, the location of the kingdom of Rheged has long been unknown. Previously, historians thought it might have been centered in Cumbria, a county in northwestern England.

Bowles and Toolis laid out the excavation’s findings in their book “The Lost Dark Age Kingdom of Rheged,” published this month. As Bowles puts it: “This was a place of religious, cultural and political innovation whose contribution to culture in Scotland has perhaps not been given due recognition. Yet the influence of Rheged, with Trusty’s Hill at its secular heart…and Urien its most famous king, has nevertheless rippled through the history and literature of Scotland and beyond.”