We built a digging pit for Jax with sand about 6X6. He loved to.dig in it and knew where to dig because every morning we took him there and said playfully lets dig. At first we buried toys and treats in it but he'd dig them out and not stop digging. He loved this and then at 10 months he began to dig less and less. Now it's been a month or more since he dug in it. So we are considering taking it out. Here's a picture of him in it.