Looking good there nubcake

There's a few little things I would change based on what I can see, though:
The outer walls (the rock) of that outside area need more height variation to escape that box-room feeling, especially because the area seem to be roughly square in shape, which just adds to that impression.
Some detail elements look like they really should me made with a smaller grid size, such as the railings on your walkways, which look a little too blocky at the moment. I' suggest making the vertical parts less thick than the horizontal part. Also, making them less thick altogether might be a good idea, 8 units(I think?) is a bit too thick for that kind of thing imo. Same thing goes for the girders, like those in your second shot, above that cave entrance. The uniform brush thickness looks odd.
The lack of 3-point-clipped detail elements is quite obvious as well. I'd recommend bevelling some edges, although this is entirely up to you.
Overall, looks like it has potential, keep it up, you're definitely improving
