Two of my three cats, Oreo and Cookie, are pretty adventuresome and really want to be in the great outdoors. Unfortunately, it's just too wild around here with fishers and other critters. Plus I live pretty close to a very busy road.
So safety first and the sisters spend their day in the cat run, which is about 6 ft. high by 5 feet wide by 10-12 feet long. There are wooden boxes to play in, and greenery to eat. They really like it out there. And I have peace of mind.