English: Shelter for the Maragheh observatory, Maragheh, Iran. Its structure is a geodesic dome based on an Icosahedron. The triangles of the Icosahedron are marked in red. Note that there are five triangles at points where the red triangles meet, otherwise there are six triangles at each meeting point. If the dome were extended into a sphere and all openings closed, there would be 64 small triangles in each of the 20 red-bounded larger triangles. A hemisphere would have 5 larger triangles meeting at the top with the remainder of the dome made up of similar triangles that have been sliced where they meet the ground.