Pentagonal Rotunda (J6)
One of the 92 Johnson solids, which are non-uniform convex regular-faced
polyhedra. This one has 5-fold pyramidal symmetry, and may be thought of as one half of an icosidodecahedron.
J6 has been useful in constructing Stewart toroids, such as the
drilled pentagonal rotunda, the
rotunda-drilled truncated icosidodecahedron,
and this more recently discovered
genus-41 Stewart toroid.