This is the double-helix modern spiral stair in the restored historical tower of the Ljubljana castle (Slovenia).
Notice that this is in fact two independent embeded stairs!
Shot on film
I had to extend my arm (with my Pentax LX camera) between the red bars up to the center of the well, so i couldn't see anything in the view-finder. Well, i kind-a could see just a little bit because i took off the view-finder prism (wonderful LX!), but still... Would you call that a lucky shot? :)