I don't understand why you'd want a spiral staircase cast in concrete, but that's probably because I couldn't afford to have one made. An anonymous client of architectural design/build firm RAP did, and the firm's execution is pretty darn impressive.

"We are based in Rotterdam," the firm writes, "where we surround ourselves with robots in an industrial atmosphere where we can discover and realise challenging architecture."

Spanning two levels, the entire thing was not cast in one piece, but each floor-to-floor unit was.

"We set up a parametric design to make such a complex and beautifully detailed project reality. This efficient digital workflow made design and optimization changes very easy. This way we added essential value to this project which led to the realization of this unique single concrete casted staircase."