It's hard to tell, aside from the signs on each building, what they hold; few beings other than demons ever enter or leave them. Those that aren't tend to be very well-off-looking mortals; powerful wizards or slavemasters, mostly. The buildings, likely, contain what their name indicates; a prison, torture rooms, beings kept specifically to be slaves, or to be broken as slaves, either beings kept to be 'toys', beyond broken as slaves, or any number of horrendous things that might be used on captives, beings kept for breeding, creatures kept as pets, likely like the tentacle-hydra in the arena, a building that might either hold food for the captives... or turn them into it, and buildings for processing those coming in and out.<br/><br/>The building are large enough to hold a thousand people, easily, if not many more, depending on how cramped they are. He can see nearly eighty demons or evil mortals in the main areas, giving the impression that there's likely a few hundred or more, between all the buildings.