This looks really cool. But it's very very dark, hard to see all the hard work you put into it. Generally I like to avoid pure blacks, since it's really just filling the frame with a whole lot of nothing. You can still get dramatic lighting without crushing all the shadows into nothingness. I'd suggest adding a soft…
Hmm well let's back up a bit. Do you have a particular photo reference for this site? It would help to have the guidance of a real-world location to help you achieve realism & believability. Here's an example of a stonework vault: The stones between the ribs don't just tile along under the ribs, they're integrated…