I'm just wondering how Large Halls and Indoor Arenas are defined?

I see in Sao Paulo a gymnasium that could be considered to be Arenas in the Large Hall section and I've just had smaller gymnasiums approved as Indoor Arenas.

It's just messing with my mind a little. :D

I want everything to be organized into their proper sections.

For me a Large Hall is a venue with seating like a theatre, (not designed for sporting events specifically) a building or large room used for meetings, concerts, or other events. An Indoor Arena is a venue which is unsurprisingly indoors and is a level area surrounded by seating, in which sports, entertainments and other public events are held. Stadiums are like Arenas, (a level area surrounded by seating) but they are outdoors. E.G. I obviously classify the Colosseum of Rome as a stadium.