Genus: 4

Symmetry: Multi-directional

This model from a vertex figure suggested by Don Hatch
is not easily seen as a space packing of polyhedra, though it can be constructed
as a packing of octahedra and tetrahedra with some faces removed. . It
is particularly beautiful being composed of flat snaking paths of coincident
triangles that stretch to infinity. The paths come in four different orientations,
each shown here in a different color. The result is an impossible seeming
figure that looks very much like the intersecting staircases in M.C.
Escher's "House of Stairs" lithograph.