I have a really big two-story “condo” cage for my two small (Polish) rabbits, I forget the exact dimensions – I’ll have to go get a measuring tape – but it’s close to 4′ x 3′ x 3′ counting two stories, and has a total of some 24 square feet of floor space (not counting the ramp between floors). In addition, they have a large exercise pen, adding on another 24 square feet or so of floor space, which is always up for an 8- to 12-hour solid block of time in every 24-hour day. While they’re confined to the condo cage during the daytime when I’m away, rabbits do most of their sleeping and resting during daylight hours so it’s not a problem, and they have the greatest possible amount of space available to them during the evening and overnight hours when their pen is erected. It does help that they’re so little (3-4 pounds each) so that they’re able to live comfortably in more space-limited circumstances than bigger buns.