Access To Underground Place On Emerald Trail

Hy,
So basiaclly there is a wooden house along the emerald trail just before the "Grind Spot" (it's hidden behound the mountain on the map) and there is a ladder down to a brick basement with two levers (than won't move for me) and a skull ontop some magma, and I can see and hear there is a large room behind the wall (has Mutated villigers along some other enemies in it).
How can I open/remove the wall and enter it?

 

There is a house on your left when coming out of Detlas, opposite side of the grind spot. Go to the little shack looking thing on the right of the house, with the stairs leading down. The floor will collapse and there will be a button in the pit you fall into. Click that and voila!