Avidius Cassius

Hi, i'm new to the site and have to do a project about gladiators and i had a question concerning the topic. We all know about the Roman Collesium, but what about the other arenas where they fought? I have to imagine there are a bunch, but all you hear about is how great the Collesium is and nothing about any others. So are there any other notable arenas that even come close to the popularity and/or size of the Collesium?