This is another variant on the fougou-style of mapping (see eg previously), along with a different sort of hatch pattern that doesn’t overwhelm the detail in the walls.
The stair marks are, I think, backward from what is conventionally used to note stairs leading down (presuming that this is a warren of underground rooms with one passageway up to the surface and not something weirdly being accessed from below).
There is a kind of secret door implied in the lower right, where there is a wall that covers over an alcove directly behind. If that large stone was on a pivot or hinge, it could be a secret passage. Even if not, it could be something that adventurers could discover and pry open, if they were so inclined.
No doors are shown in the plan, but there are jambs that could be doorways at the transition points between rooms and the more tunnel-like passageways.
As usual, feel free to use for any non-commercial purpose, or contact me if you’d like to use this on a commercial project.