Traditional circus tent.
It's also worth asking Circus Ferrel.
Many years have had complaints that the big top has been too small (and thus not everyone could see every show).
On the other hand, a top that is too big will be MUCH more expensive, can have a very negative effect on the atmosphere in the tent, and will be extremely hard to heat. Nobody likes sitting freezing to death in a big top, and no performers like playing to a half empty tent.
Tents are vulnerable to weather and MUST come with either an on-site tent master, or some way to contact the tent company 24/7 to bring someone on site quickly if the weather starts to cause problems. A big top in unsuitable weather is an enormous health and safety hazard.
Tents will require lighting, sound, heating, staging, and battery backed fire exit signs; the tent provider can usually quote for bringing and rigging some or all of those. Banked seating is more pleasant than sitting on the floor, but will reduce capacity dramatically.
You might need space for people to queue for shows without blocking access to other parts of the site.
If you want to rig aerial in there, you need to speak to the person who will rig the aerial and to the tent supplier beforehand; it may be necessary to do some of the rigging as the tent goes up.
Big Tops need to be delivered by big lorries (depending on size), make sure they will be able to access where you intend to erect it.
Make sure your contract includes
- the size of the tent
- the specific footprint if that is important for your site
- any AV, seating, heating, staging, fire exit signs, aerial rigging
- how they will support you during the event if things go wrong
- any requirements you have about when they can be on site to rig and derig.
- the power requirements of any lighting and sound they are bringing (both wattage and connectors).
- when they will need to be on site, when the big top will be ready to use, how long they need to take it down, when they will be off site
It's a good idea to get compères to ask people to refrain from pissing on the tent (an attractive proposition to drunken men in show intervals). Maybe positioning toilets not too far from Big Tops if possible will allow people to get to them, to queue and get back in any show interval.