Church of Our Saviour on the Spilled Blood, St Petersburg, Russia. As a ghost, I am looking for a castle to haunt. What about this one? I know it isn't technically a 'castle' but look at its magnificent size! I think it would still be splendid to haunt.
Pedraza is one of those medieval small villages you can get from Madrid for a daytrip. Its "The Night of Candles" takes place one night per year in July, when there is not unlit a single corner of the town.