In geometry, the 25 great circles of the spherical octahedron is an arrangement of 25 great circles in octahedral symmetry.[1] It was first identified by Buckminster Fuller and is used in construction of geodesic domes.
The 25 great circles can be seen in 3 sets: 12, 9, and 4, each representing edges of a polyhedron projected onto a sphere. Nine great circles represent the edges of a disdyakis dodecahedron, the dual of a truncated cuboctahedron. Four more great circles represent the edges of a cuboctahedron, and the last twelve great circles connect edge-centers of the octahedron to centers of other triangles.