This is joint work with Henry Segerman (www.shapeways.com/shops/henryseg). It models a regular space-filling tessellation of hyperbolic space (one of eleven exotic tessellations that have infinite cells and/or vertex figures). In this case, the cell is a hexagonal tiling, and the model is vertex-centered. Three cells meet at every edge, and four cells meet at every vertex. For more details, see Coxeter's paper, "Regular Honeycombs in Hyperbolic Space"