Don't know if this is a new discovery, but you can see a castle in the distance in the Nightmare Frontier : r/bloodborne
Rate my nightmare frontier skip ! Who knew the nightmare frontier was always on the edge of a dream. I only added music and sped up some parts. Where the skip ended
Nightmare Frontier | Bloodborne Wiki
Bloodborne Guide - Lecture Building, Nightmare Frontier, Amygdala Boss Fight - Prima Games
While i was wandering Nightmare Frontier, i saw a bunch of decrepit ships on the edge of the map. I even took a screenshot just because i find it really interesting, they
Bloodborne - Walkthrough Part 12: Nightmare Frontier - YouTube