The library at Mafra National Palace in Portugal. Where, to keep books from being damaged by insects, they uses 500 bats! The bats are kept in boxes during the day but at night they are let out and eat up to double their own body weight in insects. (Info taken from this article at bookwire. Thanks to amygarvey for telling me about it!)
I think I need to go there. Do you think they’d notice if I moved in?