Most RPGs these days basically ignore level design altogether, crafting open and often lovely environments and fairly linear, unimaginative dungeons, as though this coupling of above-ground openness and bel0w-ground linearity will result in something akin to diversity.
The design here is impeccable, a truly ambitious and exciting and gorgeous display of building a linear game that is not linear, an open world that is not open, filled to the brim with secrets and wonder.