| Hierophantasm |
Funny you mention it...my players thought the same way. One sent an arcane eye up there, and had me on the spot to describe what he saw. (Ugh, improv.) Anyway, I winged it, but a handy map wouldn't be a bad idea.
While I was sad to see Wil Wheaton's column leave the pages of the magazine, the Maps of Mystery are quite useful. The one in issue #132 is of a coaching inn--not really a castle--but it might be useful. It even has a cellar, which could connect to the arena understructure via a secret door--wouldn't be the first one.
On the whole, try to do all you can to discourage their presence up there...say, with the threat of expulsion from the games, or prosecution, which wouldn't be tough given Loris Raknian's social standing. The PCs should understand that they have no business there, but PCs are PCs, and if they are determined, they will find a way.