An Elven Castle

"The sun was low when they came back to the island. A thin mist lay over the sea, diffusing light, making the high walls of Tyre golden, not altogether real, like an elven castle that might at any moment glimmer away into nothingness." (Time Patrol, p. 298)

This scene should be filmed to look like that, as if the story were fantasy, not historical sf. Everard might, at any subjective moment of his career, make a time jump that takes him into a timeline where Tyre has never existed and therefore seems to him to have glimmered away.

When Gratillonius first sees Ys:

"He could scarcely believe that human beings dwelt yonder, not elves or Gods."
-Poul And Karen Anderson, Roma Mater (London, 1989), p. 104.

The Ys tetralogy is historical fiction with elements of fantasy. Thus, the Gods veil Ys. When the fabulous city with its colored towers and Elven Gardens has been inundated, even people who lived there wonder whether it really existed.

Thus, there are some parallels between Everard's perception of Tyre and Gratillonius' perception of Ys. Ys is a colony of Carthage which is a colony of Tyre.