Stairs?

[Jaxilon]

Looks pretty good to me. The thing is all the talk of shadowing totally depends on the light source. If you put a slitted window or a torch/lamp in somewhere everything is different.

If the light was coming straight down from the top things wouldn't be darker near the center column but would have a more even distribution across each step with the ones near the bottom of the staircase a bit darker over all than those nearer the top.
If the light is near the top of the stairwell (as in on the landing) the center column would throw a straight line shadow and pretty much everything below that would be in darkness or nearly so. You might have some reflective light bouncing down a ways but nothing really great.
A window slit or lamp half way up would look the coolest but then you would have the brightest part of the stairs being at the halfway point and more shadows farther down and up the stairs.
No light, in an enclosed spiral staircase is probably just a great way to break someone's neck.

Your stairs get the point across very clearly however and I do not think any gamer would mistake what they were looking at.