Leaving Ys

The departing defeated Scoti see the city:

"High and high the walls gleamed, and the towers beyond; it was as if the voyagers had truly crossed Ocean and come to Tir innan Oac. The very rowers stared and marvelled as they toiled." (Roma Mater, p. 285)

See here.

As if they had crossed Ocean and seen Tir na nOg or as if they had crossed Ocean and Time and seen New York.

When an Ysan bolt has killed his son, Niall curses the city:

may the sea rob its King of what he loves;
may what he loves next turn against and rend him;
may the sea take Ys;
may he, Niall, be the agent of the wrath of the Ysan Gods;
he will pay any price.

All  this will happen.