A city and castle.

This apparently was the major castle of King Ban, in France. Near Trebes was Bois en Val, site of the “Lake” where the Damsel of the Lake raised Lancelot.

Malory identifies Benwick, King Ban’s country, as Beaune or Bayonne. There is a city of Bayonne on the coast at the southwesternmost part of modern France, just north of the Pyrenees. Perhaps eighty miles east of Bayonne is a city called Tarbes. Could Tarbes derive from Trebes?