Well, I have 6 cages. mainly for the culls. (because sometimes it takes me awhile to dress them out lol!)
But, overall, yes, I have a rabbit "pen". Works wonderful. We built a pen with welded fence wire, 4' tall. It is buried about 6" into the dirt. We have lots of trees and sand, so I didnt add anything to have a burrow for the bunnies. It actually took about 4 months for them to figure out - or for their instincts to kick in - about digging burrows. The females go into their hole and make a nest, birth the kits, and we dont see them until they come above ground to nibble on feed. I have an automatic waterer (like for a dog) and some bottles hanging around the fence. I did have to go back and put 1" chicken wire on the bottom of the pen, the little ones were hopping out and my dogs were getting in the habit of chasing them. (hence - two bad dog attacks, by our dogs)
As a result I now have two farrel bunnies, one california and one black bunny (rex mix) I will have to get a live trap to get those two back in the pen, they have grown up on the lamb
For me this is perfect. My rabbits pretty well come up, especially when I call "here bunny bunny bunny"

They love to take range cubes (be sure it is the kind you can give a horse) from my hands, a special hi-protein treat for them. We often toss in the tree trimmings from our heavily wooded acreage. They love to chew on the bark/leaves. Especially sweetgum trees. Anyway, they have chewed the bark off all the trees in the pen for about 1 1/2 feet up and I will probably have to go cut a bunch out. I do release the male for breeding. The only problem I have is, if I dont get the babies up fast enough and sex them, the males will neuter each other. (makes nice fat bunny-roast tho!) I will put in three links, one of the first "old" way that we kept rabbits. We had a dog destroy the cages and kill all but 3 rabbits. (we had 15 at the time - two large litters) So, we then built the "pen" and have only lost a few rabbits at a time when dogs attack, the rabbits run to the holes and hide, they have learned to dig real deep.
the pictures load slow, they are large. also, the cage and topper you see in pic#1 is now installed in the pen for our "culls" .
hope that helps!
http://mamajohnson.com/main/pics/bunnies.jpg
http://mamajohnson.com/main/pics/bunniepen3.jpg
http://mamajohnson.com/main/pics/bunniepen2.jpg