1,2 Icosahedron by Steve Morse.
The icosahedron is one of the five Platonic solids. Its twenty faces are equilateral triangles, with five meeting at each corner. In the model above, each face is further divided into six congruent 30-60-90 triangles, for a total of 120 triangles. The model is constructed from 15 slotted rings lying in 15 planes.
Photos by I. Peterson