This ambience brings me back to the first time I played the C/D route. My brain keeps remembering "r-r-r-r-revenge f-for our k-king-g-g-g!" Oof this route was rough and full of feels
To be honest, it seems bizarre to me that such structures as a medieval castle can exist after several thousand years in the world of Automata. Even nowdays, medieval castles are being slowly destroyed by time, never mind weather. The only possible explanation I can think of is that this castle was constructed in the present day world or even later, with some kind of new materials that can withstand several millennia.
I always figured it was built sometime in the several centuries long post-apocalyptic period following that Replicant and Gestalt were set in after everything gets End Of Evangelion'd in Drakengard ending E.
From what I understand, the machines themselves supposedly built this as a fortress to protect… something. I’ve only played through the part where this is explained once (to avoid spoilers, it’s your second playthrough of the game) so I’m probably hazy. All I remember is thinking once “how could machines build all THAT??”