The Platonic Solid like you've never seen them before..
Tetrahedron, Cube or Hexahedron, Octahedron, Dodecahedron & Icosahedron.
Each Geometric shape is looped around its self in a unique complex, eye boggling way - Each shape is also one piece.
I've put them all in one STL file, each is 100mm in size and wall thickness is 3~4 mm.
3D Print them with various plastics or Stainless Steel.