Come to think of it, now that Sorcerer's Deep has breached 50,000 people, we could technically expand the Circle of Battle into a full-on Colosseum sized affair. It was estimated to host audiences between 50,000 and 80,000, with average occupancy of 65,000.
Meaning we could just about fill it with the entire population of SD, still have room for more, but without it obviously making apparent how small SD is compared to its ambitions (and I think having just moved in over 10,000 people in a single month, with no signs of stopping or slowing down...).
Edit: Ah, modern estimates were put at 50,000, actually, not a "between X and Y" number. Makes sense.