Feudal Britain seems to have been a very complicated place in Arthur's time. Their are dozens of other kingdoms mentioned, and Lugodoc sees them as divided into three main categories:
Almesbury - site of nunnery 30 miles from Glastonbury, where Guenever died.
Aramathie - biblical city in the Holy Land, AKA Aramathea.
Arroy - a magical forest and country 7 days ride from Camelot, and home of the goddess.
Astolat - old name for Guildford town.
Avelion - AKA Avilion (known these days as Avalon). A possibly magical realm, & home of the Lady Lile, & also of Dame Lionesse & her brother Gringamore.
Avelion, the Isle of - close by the Castle Perilous.
Avelion, the Vale of - a place of healing, & almost Arthur's last known destination until his uncertain diversion to Glastonbury (which may be the same place).
Bedegraine, castle & forest - site of Arthur's second battle in Sherwood Forest (against the eleven kings and one duke).
Benwick - French land ruled by Launcelot's father King Ban.
Bliant, Castle - Launcelot's place of exile as Chevalier Mal Fet, after his madness but before his return to Camelot.
Brittany - peninsula of Western France. AKA Little Brittain.
Cambenet - home of the Duke.
Cameliard - country somewhere led by King Leodegrance, & site of Arthur's 3rd battle.
Camelot - a castle city, now known as Winchester, & Arthur's most famous seat.
Carlion - site of Arthur's first battle (against the six kings), and later one of his seats. Probably Caerleon, site of an old Roman fort and amphitheatre in South Wales.
Corbin, Castle - Seat of King Pelles & his daughter Elaine, & birthplace of Galahad. Highly enchanted, containing many wonders including the Sangreal, the Spear of Longinus (or Vengeance) and a floating silver sword. AKA Castle Carbonek or Castle Adventurous.
Corbin, Land of - ruled by King Pelles.
Corbin, Point of - distant place marking the beginning of the Land of Corbin.
Dover - site of Arthur's 9th battle, against Mordred.
Dover Castle - resting place of Gawaine's skull.
foreign country, the - King Pelles' original homeland (before Corbin), presumably Palestine.
Forest Perilous, the - a place of adventures in North Wales.
Galis -the Southern & lesser part of Wales.
Garlot(h) - land ruled by King Nentres.
Gaul - Roman name for France.
Glastonbury - town & abbey, & supposed resting place of Arthur.
Gore - a land near, or possibly in, Logris, ruled by King Uriens & Queen Morgan le Fay.
Hard Rock, Castle of the - site of major joust. AKA Roche Dure.
Humber - site of Arthur's 5th battle in a forest near the River Humber against 5 kings.
Ireland - ruled by King Anguish and/or King Marhalt.
Isles, the - home of King Pellinore.
Joyous Gard, Castle of - Launcelot's English seat, in either Alnwick or Bamborough
Kynke Kenadonne - city & castle in the sandy Welsh marches. One of Arthur's seats where he liked to hold Pentecost in his heyday.
Lanceor & Colombe, tomb of - King Mark built this dead lovers' tomb near Camelot, and fulfilling Merlin's prediction Launcelot & Tristram fought there about 20 years later, "the best knights in the world and the truest lovers".
Listeneise - land ruled by King Pellam. AKA Listinoise.
Little Britain - AKA Brittany.
Logris, Realm of - olde Celtic term for England. AKA Logres.
Lonazep - site of a major joust on May Day. Near to a Round Table seat & Joyous Gard.
Long Isles, the - ruled by Prince Galahalt; possibly the Hebrides. AKA Surluse AKA Soleise.
Maidens, Castle of the - site of major joust, then later saved from wickedness by Galahad. Possibly Maiden Castle near Dorchester ?
Northgalis - the Northern & greater part of Wales. Home of king & queen who, though never at war with Arthur, were his main rivals at jousts.
Northumberland - land in North of England bordering Scotland. Home of Merlin's master Bleise, and of the poor knights Balin & his brother Balan.
Orkney - islands off the North coast of Scotland ruled by King Lot & Queen Margawse, and home of their sons (& bastard), the Orkney Knights.
Outer Isles, the - probably a general term for the Hebrides, Orkneys & Shetlands.
Perilous, the Castle - home of Dame Lionesse beside the Isle of Avelion. AKA the Castle Dangerous.
Perilous, the Chapel - final resting place of Sir Gilbert the Bastard.
Red Launds, the - home of Sir Ironside the Red Knight.
Salisbury - site of Arthur's 11th & last battle against Mordred, near the seaside.
Sarras - ancient foreign city near Babylon where Joseph of Aramathie converted King Evelake to Christianity, and much later Galahad was imprisoned, then made king and died. Last known sighting of the Sangreal & Spear of Longinus.
Sessoine, vale of - site of Arthur's 6th battle against the Roman emperor Lucius, somewhere in Europe.
Soleise - possibly the same place as Surluse.
Stranggore - land ruled by King Brandegore, possibly near Gore.
Surluse - AKA the Long Isles AKA Soleise.
Terrabil, Castle - in Cornwall. Site of Arthur's decisive 4th battle against the 11 kings from the Battle of Bedegraine plus King Nero.
Tintagil, Castle - in Cornwall. Arthur's birthplace.
Vale, the - a territory within Logris ruled by a king.
Wentland - home of Sir Ontzlake.
Westminster - Arthur's London seat.
White Abbey, the - resting place of the Shield of Joseph and King Bagdemagus, and other wonders, in the land of Gore.
Winchester - AKA Camelot.