I've read where in one really long day you can do Jerash, Ajloun and the Desert Castles but that seems like a ton of driving. Just how cool are the Desert Castles? ;). If it is really neat then the thought I had was to only go to Qasr Al Hallabat - it says its 60km from Amman but how long does it take to really drive that distance? I'll be there in May.