This place actually begins before you even arrive. When you're still down below, near the Crumbling Factory you'll feel yourself compelled to head north, and you won't be able to continue until you go.
Once you arrive at the Great Circle and are nearing the middle you'll feel compelled to approach and destroy the altar. You don't have a choice, so you may as well do it anyway.
Once you've destroyed the altar several Haakai will appear. They will demand that you give them all your items. Refusal results in them summoning quite a few Mung Demons to help them, but the battle is good for experience.