The rest of the house. @cookieman wrote it before me.
My husband has a man cave. He is going to put his awards he has won in there, some of his racing photos, his model cars, and a big TV. Also, he keeps the files he deals with stored in there (as opposed to the office I have set up in another room) and he can do whatever the hell else he wants to do in there.
Our house is not decorated without his influence though. We choose everything together. I tend to have a more masculine and minimal taste myself, so it’s not like the house is feminine except for that one cave room. My office, which is my cave I guess, is where I can have piles of crap I have not dealt with yet and he can’t really say anything. Not hoarder level, but my office is never neat as a pin. I guess my office is my junk room. I’d rather our house have a man cave room have a formal living room no one uses. That’s what we opted for in this new house we are building.