Several years ago when my son was young, we filled one of those hard plastic
molded swimming pools full of sand as a sandbox.  I let my ferrets dig in
this, they loved it.  There was no walls to dig under, the sand was soft
enough (and cleaner than dirt) but if you get it a little wet, it molds and
keeps a tunnel formed when they dig.  This is a great way to let them dig,
stay cleaner, yet can be used over and over, without ruining your lawn.
 
Cathy
[Posted in FML issue 1586]