Add holes, rifts, windows going somewhere- you can listen on them. You can look into them..
Also just add awareness that something might be wrong..
"The plates of the floor sound hollow or soft"..
"The room seems to pulse slightly, in the corner of your eyes."

Very Lofecraftian but always funny - "Inconsistent Perception"..
"You find a huge wardrobe on the other side of the wall".
"I want to look at the wardrobe."
"There is no wardrobe here-"
"You realize, that you are hugging a huge stone obelisk in the shape of a wardrobe, covered with the blood of sacrifices."

Also Cobwebs,hiding everything, blowing in the wind - "You see a huge golem- covered in Cobwebs"
"Attack"
"You see some Cobwebs blowing in the Wind.."

Also fun- thread the thing to be a deathtrap or one-way.
"The orks who build this- seem to have taken no great care to hold back earths pressure- dont touch the rotten beams. Every step seems to make them swing slighty."
(Better not cross the room alt at one - :)