Bottom left of the black trench you can climb the wall onto a black invisible area, at some point you just fall to your death if you keep walking into the void.
I was looking for the square room here, Thomas last inverview where he showed the entire map in unity for a bit. Well I quess I found the roof of the square area 
*Still not found a way to get to the northen part of the map, but i think its not in the game yet 
Anyway video below:*
