Castel de la Marche, Castle of the Marsh, March Castle, Marche Castle
A castle ruled by Count Bedoin.
During the Grail Quest, Galahad besieged March Castle to stop Bedoin from disinheriting his sister. Bedoin was eventually defeated.
Since King Brangoire was holding the anniversary of his coronation here, and since the Vulgate’s Brangoire is Malory’s King Brandegoris of Stranggore, this castle would be on the border of Stranggore.
Source
Post-Vulgate Queste del Saint Graal | 1230-1240