An icosahedron and twenty tetrahedra
A regular icosahedron, divided in twenty tetrahedra. The tetrahedra are not regular: if they were regular, there would be five regular tetrahedra around each edge and the these ones can't tessellate the space, because the dihedral angle of the regular tetrahedron is smaller than 360°/5.
From the exhibition "Riflessioni & riflessioni", held in Turin.
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From the exhibition "Riflessioni & riflessioni" in Turin (Other exhibitions around the world)