I have no idea about “favorite”, but a nice memory that immediately comes to mind…
My dad was a minister, when I was little we lived in the “parish house” behind the church. Decent sized church. I have great memories of going up in the attic of the church - all sorts of catwalks and different “rooms”. And once my dad sent me all the way up the steeple, into the really narrow part with ladders & trap doors that was hard for an adult to get in. (I think he was having me check if there were any leaks?)
Always loved weird nooks in large buildings. Attics, cupolas, forgotten rooms, etc.