I got my mouse a pink CritterTrail cage and was trying to decide if I wanted to get some extra tubes for her to run around in. Then I saw this thread and how crowded (in a good way) a lot of people's set ups are and decided to build her a loft instead. I made it out of bird perches and some fleece. She seems to like it and hasn't tried to tear it up! I'm not sure if she actually uses the ladder to get to it (I know she can use the ladder) or if she just runs up the bars of the cage. She also has a bird toy in the back corner there that's full of coconut fiber for nesting. She hasn't tried to pull out any of the fiber, but she likes to run up and down the colorful wooden rings on the outside.