Got a wooden fence around the bottom for the litter to be deeper and a fish tank dig box filled with safe dirt (ask if you want to do this to) This set up have only 2 real levels forcing my boys to actually move and exercise to get where they want to be :D i have an ikea tie rack in their as well as a wood and rope bridge a wooden branch for birds and a few baskets and buckets put up for beds and steps :) oh yea and some colorful chews!