Thanks again everyone for the valuable feedback.
I have removed the horrible stairs and replaced them with rough stairs made from the same rock as the floor.The stairs in the bottom left corner don't look right. I can't put my finger on it, but I think it has to do with the lighting/shadow of them and the fact that they don't look "natural" or even as something constructed.
I have darkened the rock texture and added a bevel to it to try and take away the jarring impression cused by the meeting of the rock texture with the cut-away areas.1) Try making the wall/rock texture significantly darker.
2) Try applying a slight bevel to the wall/rock layer. This will hopefully make for an easier transition between the wall and floor layers.
I have also lowered the opacity of the shadow layer as has been suggested by several people.
I think these changes improve the map.
Torq