I was thinking the arena was more of a large, public square at first but was converted into an arena recently. It could be used for public trials and as a coliseum now that it's been converted. There could be cages/prison areas that they keep the combatants in that open to the coliseum itself.

It probably isn't used that much though just yet since things are fairly peaceful among the people. The King or noble houses could request that hunters go out and bring back some creatures to be used in the arena.

By the way, [@AtomicNut] Leon's profile is good. You can go ahead and post it.