Ahem. Anyway. The one I eventually decided on was technically outside the age range I was looking for, because the earliest records of inhabitance were from 1476. I fudged it under the logic of, "Well, it wasn't built in a day, was it?" I just decided to assume it was older than that record and could feasibly have been in use in 1431.
Eh, time gets wonky in Singularities. This wouldn't even be the strangest anachronism in FGO.
Better yet, that detail was thought up in order to justify exactly the this sort of thing.