Are you talking about UGntended?raves
In Dark Souls 1, there was a place with an illusory wall, then behind it, a chest, then behind the chest, another illusory wall which led to a gigantic area.
Since then, I check every wall behind every chest. Which has gotten me two illusory walls in this game.
They're talking about the
Archdragon Peak
use a specific gesture at the edge of a certain cliff
I finished in 30 hours, and while it's true to some degree that I left some areas unexplored, ain't no way I would need 20+ more hours to get the items I missed the first time around.