Some of our kids dig for China, Bart with big paws acts like a steam shovel. We use storage bins that are about 18 inch tall, I cut one the end out with about 6 inch remaining, this keeps most stuff in the box. There is one in the bed room and they will take turns using it just before going to sleep. So for about 30 minutes all you hear is digging.
Then there is Princess she will go then walk on the top edge of the box. It's funny watching her try to reach the litter without touching it.