Put in a digging pit for rabbits. Nothing fancy. Just a tub filled with soil or sand so that they can dig to their heart's desires. This may curb their desire to dig their way out of the rabbit run. #rabbits
I tried this with my bunnies hutches with irrigation pipe and drilled holes in it to filter out the pees and poops. The rabbits absolutely love it! It's nice and dark and they just chill in there as they see it as a safe and spot.