This is something I came across in a book on snakes and reptiles. The author suggested using a clear polycarbonate enclosure that had two doors, one on the side and one on top. You would then use paper mache and concrete to form a burrow in the half of the enclosure that had a door in the side, of course leaving a hole for the animal to get out into the "outside" section of the enclosure. The side with the burrow could be cleaned easily when it came time to do so because of the door, and the animal could be observed easily. Has anyone done this? I would like to try it at some point.