So I believe too... Imagine them somewhere there where the stream comes from which moves the wheel before it falls into the crack. Bronze Doors are used to lock the Stone Labyrinths and its dangerous creatures from Yliakum. There are several, the Eagle one is the closest to Hydlaa (and possibly a kind of "north" point in an imaginable map of the currently implemented world, as you can see on the intermission screen when you travel with a Pterosaur).