I definitely agree with the reply above, rats love clutter! I usually go to my recycling bin and grab some cardboard boxes for my boys to hide in. I might also suggest a digging box. You can use paper scraps, those craft puff balls, anything really. Sprinkle some treats in it to encourage them foraging. Used dog toys, if you have a dog or a cat, can also be a fine addition to your rat’s cage! It looks great so far!