The spirals in a shell are logarithmic spirals, different from the one which is shown here, which is an archimedean spiral; we can see archimedean spirals on many buildings in Bolzano, for example palazzo Widmann, where we find one of the ten maths signposts of the project MIC "Maths in the City", in Bolzano, where this image has been used.
immagine di Ester Dalvit
The image belongs to the sections...:
Some images of the maths signposts (Exhibitions with matematita)
Curves and lines (2D geometry)