These are places in the evertii forest. In the really hard to-find-core, only Bowling Bulb and fish can find the way in.
How it looks like
A small room out of iron, inside it : a bed, oven, water, chest with food, door *to exit* and that's it.
x : 3299
y : 95
z : 421337
Note that nothing can display coords in Evertii Forest - these coordinates were estimated.