COMPOSITION
I really like how you have composed/cropped this shot. You didn't try to include too much which would have taken away the wonderful detail, but you left enough for the eyes to have something to follow "downwards."
TECHNIQUE
The focus on this is great, and you have used the available lighting to your advantage. It would have made this shot more immediately appealing if there was light on the lower levels, but if it were coming from above it would blow out the upper level, and I think it works okay the way it is. The darkness, getting "thicker" as you go down helps to anchor the shot and really sets up nice contrast with the upper levels. I like the colors, and I think this shot works well in color, but out of curiousity, I was wondering if you tried it in black and white with a lot of contrast. I don't think it would make it better, but it would be interesting, I think.
OVERALL EFFECT
This is a shot that literally draws you into it. Very well done, and I enjoyed it. Sorry I could not offer more in the way of improving it, because I think it is already very nicely done.
Good work and best to you in future challenges.
karmat
This could have been a "six" in the numbers challenge. Instead, you've got a beautifully composed image. I really like the way you've positioned the curve of the stairs. You might have considered some additional light further down in the stairwell but lacking that doesn't detract from this photo.
I like this shot, and would have given a high mark, but for one thing. The stairs are well lit on the top, but there is insufficient lighting farther down.