Cardueil is the city where Arthur most often holds court in verse romances and where he often holds court in the prose romances. It is often believed to be identical with the real city of Carlisle and in medieval English adaptations of French Arthurian romances is often translated into Carlisle and in many other English romances Arthur holds court in Carlisle.
Carlion, that is Caerleon-on-Usk, is another city where King Arthur often holds court.
The “Waste Land”, not the “Waste Lands'', is one of the names of the kingdom of which Carbonek is the chief city. It is also called Listenois.
Real regions in Britain that often appear in Arthurian tales are Cornwall, Scotland, Lothian, North Wales, Wales, Northumberland (probably understood to also include Yorkshire in some tales and to really stand for Northumbria), and Logres, Logres approximately corresponds to modern England except for Northumberland/Northumbria. Its Welsh form is Lloegyr, the Welsh name for England, of unknown origin. The Out Isles (Iles de Longtaine) may be the Hebrides.
Loenois or Leonois is a region name that originated as a French form of Lothian, but in the late ”Prose Tristan” and in Malory (who renders it as Liones, Lyones), it apparently corresponds to the territory of Léon in Brittany. Some Victorians identified it with Lethowstow, a legendary sunken land offshore from Cornwall. See
Orcanie is rendered Orkney by Malory which may be its origin, but is a city with its surrounding territory adjoining or within Lothian/Loenois in Arthurian tales. Sorelois (Surluse) is described in such a way that it appears to be the island of Anglesey.
The surviving medieval Arthurian tales are mostly written in French by authors who often knew little of genuine British geography and simply used some real British names rather randomly to add colour to their work, without worrying that their geography did not make sense.
Real cities where King Arthur sometimes holds court also include London and Winchester. London is explicitly identified with the Arthurian city of Logres, the capital of the kingdom of Logres, in the “Vulgate Merlin”.
Other fantasy kingdoms in Britain are Gorre, Estrangor, Garlot, Escavalon, and Carmelide. In the area of modern France there is Benwick (Lancelot’s hereditary land) and Gaunes or Gannes, the hereditary country of Lancelot's cousins Lionel and Bohort (Bors). In the “Prose Lancelot” Benwick is the Saurmarois region of Anjou-Tourraine and Gaunes seems to be the valley of the Thouet river in Poitou. J. Neale Carman, in his “A Study of the Pseudo-Map Cycle of Arthurian Romance” identifies the city of Benwick within the land of Benwick with Saumur, and the city of Gaunes within the land of Gaunes with Thouars. Adjoining the land of Benwick is the “Terre Deserte” (“the Deserted Land”), which the “Prose Lancelot” makes quite clear is intended to be Berry with its capital in Bourges. It is ruled by King Claudas, the enemy of Lancelot and his kin.
Lancelot's city of Joyous Garde in Britain is placed on an island in the Humber.
Malory claims that Joyous Garde is identical to either Alnwick or Bamborough, that Benwick is identical to either Bayonne or Beaune, and that Camelot is identical to Winchester, but these identifications are not found elsewhere and are indeed, contradicted. They may be Malory’s own speculations.
See for an Arthurian Name Dictionary that is mostly accurate and provides information on a large number of Arthurian names.