Very cool. I love the feeling this inspires, of awe and fantasy. Such a huge-looking cave area making the structure (which could be quite large in itself) look small by comparison.
I think this is perfect in itself, but one thing I think would be cool on a future version: if I had such amazing talent, I'd have put structures on the cliff-face to the left, something actually hewn into the rock face. I look at this and kind of feel like I should or could see that type of feature. Just an idea. ;^]