Astolat is a legendary city of Great Britain named in Arthurian legends. It is the home of Elaine, "the fair maiden of Astolat", and of her father Sir Bernard and her brothers Lavaine and Tirre. The city is called Shallott in many cultural references, derived from Alfred Lord Tennyson's poem "The Lady of Shallott".
Chapter nine of Sir Thomas Malory's book Le Morte d'Arthur identifies Guildford in Surrey with the legendary Astolat:
And so upon the morn early Sir Launcelot heard mass and brake his fast, and so took his leave of the queen and departed. And then he rode so much until he came to Astolat, that is Guildford; and there it happed him in the eventide he came to an old baron’s place. _Wikipedia