When my cat came home after having emergency surgery, we needed a safe place for him to recover quietly and stop him from jumping until his incision healed. Have you ever tried to stop a cat from jumping? It's not easy! At first, we tried keeping him in the bathroom, but he wouldn't settle down. So we came up with something that worked like a charm:
Under our bathroom sink, we have a 3 door wide cabinet. It has new contact paper and I've always kept my cleaners in dishpans so it's very clean and safe. We took the middle door off by unscrewing the hinges and zip-tied sturdy wire grids where the door was. This let in air, light and ventilation; and also let us peek in to check on him.
Behind the far-right door and under the sink drain we put his cat box without a lid (the door made it easy to clean his litter!). We kept the "litterbox door" open for easy access when we let him out of the pen for brief periods. Behind the door on the left, we folded up a soft comfy blanket for him to sleep on. (This is the door we open to let him in and out of the pen.) Behind the middle door (the one with the open-grids) we placed a bowl of water and a bowl for food.
We never "made" him go into his pen, but instead bribed him with treats. This way he actually enjoyed going in and staying there. This pet-pen has enough room for him to walk around in and to stretch his legs. At first, we had to bungee the doors shut, but after he got used to it, he actually likes it. I'm just thankful that we came up with a safe way for him to convalesce and heal safely.
Now he's doing fine, but he still likes going in his "cat-house" to sleep where he feels safe and secure, so we'll keep it set up for him. As long as he's happy, I don't mind losing the storage space for the time being. If you need a safe place to keep your pet, this is far better (and larger) than any cage or crate!