How to get a 120-cell
This picture gives you an idea of how to get a 120-cell, which is one of the six regular polytypes in 4D, made up of 120 dodecahedra, which meet 3 to 3 at each edge. You start with a stack of 10 dodecahedra (in the figure) that you have to imagine as being closed in 4D space to form a ring (just like a row of four squares drawn on paper that you can fold into 3D so as to form four faces of a cube). Then you 'fatten' this ring with 5 wheels of 5 dodecahedra each , so that you then get a bigger ring of 60 (10+50) dodecahedra. You then glue two of these rings so that a parallel of one sticks to a meridian of the other.
immagine di Gian Marco Todesco