Shot was taken in the Ludwig Maximilian University of Munich. I studied there in the 90ies.
The term “spiral” is used incorrectly for a staircase from a mathematical viewpoint, as a mathematical spiral lies in a single plane and moves towards or away from a central point. A spiral staircase by the mathematical definition therefore would be of little use as it would afford no change in elevation. The correct mathematical term for motion where the locus remains at a fixed distance from a fixed line whilst moving in a circular motion about it is “helix”. The presence or otherwise of a central pole does not affect the terminology applied to the design of the structure. (from Wikipedia)