Section - Scenery
The hole is scenery in the crypt. The description is "It is about man-sized and, as far as you can tell, the only way to exit the crypt. [A beam of sunlight] is projected down from the [hole]." Understand "opening" or "exit" as the hole. The hole is obvious.
The beam of sunlight is scenery in the crypt. The description is "[If the lamp is lit]Apart from [the lamp], this[else]This[end if] narrow beam of intense sunlight shining down from [the hole] is the only light in [the crypt]. There is [a curious mark] where it s projected onto [the floor]." The beam is obvious.
The curious mark is obvious scenery in the crypt. The description is "Someone has carved a curious symbol into the floor. It looks like a circle with a wavy line separating it into halves. There are two [small holes], one inside the circle and one outside. on opposite sides of the wavy line. Curious![first time] And what a stroke of luck that you should find it at exactly the time when [the beam] shone on it.[only]"
The floor is scenery in the crypt. The description is "The floor is made up of large stone slabs, and rather uninteresting. However, you spot [a curious mark] exactly where [the sunlight] shines."
The ceiling is scenery in the crypt.
The large stone slab is scenery in the crypt. The description is "[The floor] is made up of huge slabs of rock.[If the grave is in the crypt] One of the slabs has been raised (on what you suppose to be some kind of hidden hinge mechanism), revealing a secret burial place.". Understand "large stone slabs" as the large stone slab.