Buelt, Builth
Buellt refers to a historic region and town in mid-Wales, located in Powys county.
Nennius cites it as one of the wonders associated with Arthur: while Arthur was hunting the boar Troynt in the country, his dog, Cabal, left his footprint on a stone. Arthur piled a heap of stones there as a monument to the event. If any stone was removed and carried away, it would vanish and reappear on the mound the next day.
Buellt | 0 to the 9th century AD
Pre-Roman and Roman Periods
Before the Roman conquest of Britain, the territory that is now Wales was inhabited by Celtic tribes. The Roman presence in Wales began in the late first century BC, and the region was incorporated into the Roman province of Britannia.
Post-Roman Period | 5th – 7th centuries
With the decline of the Roman influence and the Roman withdrawal from Britain in the early fifth century, Wales entered a period often referred to as the Sub-Roman period. During this time, various Celtic kingdoms and territories emerged in Wales, and local leaders asserted control over their respective regions.
Early Medieval Period | 7th – 9th centuries
The early medieval period in Wales is characterized by the presence of multiple kingdoms, each ruled by its own king or chieftain. The region that includes Buellt likely fell under the influence of one of these early Welsh kingdoms or tribal entities. The specific political and territorial divisions during this time are not well-documented.
Source
Historia Brittonum | Probably Nennius, early 9th century