SOLVED its the power bread room from vale and its exactly the same one, i wanna know why have them on the same map

UPDATE, heres a video of it (thanks to plexa for having loads of save states on here)

So i was messing around on my game boy playing golden sun practicing retreat warp and found a hidden chest in goma cave. if you put yourself at the little part beside the pillar where you can get the golden medal and do it there then walk around the outside head left then down then right you see a room with a chest in it. unsure how to get to it or whats inside it, if anyone wants to explore feel free