I also added a vine branch to the front left corner. They are nice for climbing up and hiding under, and it gave access to the other sputnik. I eventually tied a cardboard boredom breaker tube (tough cardboard) to the roof between the big sputnik and the house roof so it gave a kind of roof run and two ways to get into the sputnik. So another great thing about that cage is, not only does it have a huge front opening door (good for taming and interaction and getting things in and out of the cage) but it means it doesn't have a door in the roof so you can tie all kinds of things to the roof and add a roof run level sort of.
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