As my memory seemed to tell me, Calgary has hosted this event before, in 1996.
http://www.rotaractorwiki.org/wiki/R...nal_Convention
There were almost 25,000 attendees for that one. It seemed unlikely to me that Calgary can even accommodate that many visitors, visitcalgary.com says Calgary has more than 11,000 hotel rooms, which doesn't seem like enough for an event that size.