look at the blocky pattern and how the rocks merge with it. It's like water dripping down and looks very unnatural. There should be a barrier between the blocks and rocks and if not, make it look less artificial. The rocks could go down and recede below the blocks to look a lot more real.
The stairwell has those 2 bars for support, but realistically they wouldn't offer much support. Perhaps have them on the corners but they go into it for added area that's connected to the stairs or even going through the center turning point of the stairs.
The large open pipes have the same issue as the blocks were the rocky walls just collide into it, and should instead have the rocks recede below the point where the pipe comes out.
The large thing of pipes have no support. There should be braces on all of them at different intervals to be attacked to the wall that they go into. They look a lot different from the 2 pipes on the top that are braced and connected their entire ride up.
The truss isn't connected to the pipe. It doesn't need to be, but maybe should be a bit smaller and loser the pipe it wraps around.
The balcony-like things with the fences seem very unnatural in that it's too far in. Perhaps the gates should be farther out, closer to the opening.