At the exhibition matemilano
In the section "Topology" of the exhibition matemilano there's an exhibit that illustrates the concept of number of crossings of a knot.
© Sabrina Provenzi
foto di Sabrina Provenzi
The image belongs to the sections...:
Layout (From the exhibitions of matematita)
Topology (From the exhibitions of matematita)
Further information:
http://matemilano.mat.unimi.it