RPG Insanity

Could someone please help me out with the whereabouts of the arena.
I have completed the true ending and yet I still can not find the arena.

Long time ago, so I may not remember correctly, but I think you just load the 2nd clear (the one with the true ending) and then you can find the arena. I'm not sure if already tried that, or if you are looking for the arena BEFORE getting the true end.