Camelot

The castle of King Arthur in the city of Caerleon. 
The castle-city is Caerleon-upon-Usk. The lands of Camelot are the kingdoms Gwent and Glywysing, and beyond (the southeast into the lands of Ergyng and Brycheiniog). 
Previously a Roman legionary fortress: Isca Augusta, or Isca Silurum. 
Camelot castle was built on the site of an older Roman legionary fortress: Isca Silurum, that Uther Pendragon and his men took over in the war with Duke Gorlois. The stronghold is known as Cair Legeion guar Uisc, the City of Legions, or Isca Augusta. The castle-city of Camelot is Caerleon-upon-Usk (The River Usk, Welsh: Wysk). 
Once an Iron Age hillfort.
The name Camelot is influenced by the Roman fortress and capital of Britannia: Camulodunum.