Do you have to build your arena on the ground floor?

title? If I want other pvp players to be able to access my castle arena to join a fight, does my arena have to be on the bottom floor of the castle and open and accessible to other players to be able to join a team and start an arena fight?

Not sure how else it would work, but also means if I want to maximise floor space I have to move absolutely everything to higher levels as soon as I want to add an arena that can accept players from other clans? :'(

Please tell me that's not the case?!