Critter Universe 3 The Wall by Ware Mfg. Hang it on a wall, or set it on a table, the "Great Wall" gives your Critter room to roam in three dimensions. Re-arrange your Critters habitat with the movable Cubes and Elevators. Add to your unit with Tunnels and a Critter Universe or Critter Universe Expanded. All Critter Universe units are compatible with other modular type systems such as Habitrail*, OVO* and CritterTrail**