I got a wire crate when I adopted the 25 pound pup who is about five years old now (and 40 pounds); she was ~ seven months when I adopted her and needed to be confined at night to not chew everything and before she was trained to the Invisible Fence collar. Once she didn't need it I considered taking it down, but my old 70 pound lab kept looking at it, then stepping in a little, and finally just started settling down in it to sleep. It's not solid like a cave or anything, it's wire, but I guess because he was crate trained as a pup (he lived with the friend I inherited him until he was 3) it had fond memories (and it's within view of the back glass door and the kitchen, so he could watch if he wanted.) It is rarely ever closed, the door is always ajar. When the old lab died I thought I might finally get that little bit of space in the den, but the little one spent so much time cuddling with the Lab in there that she still favors it to sleep in at night. And the door stays open.