This self-venting cat box by Instructables user Denver_80211 (aka Fred) really cleverly uses a built-in drawer in the bathroom to keep the litter bin vented and safe from big dogs. Also gotta love that double-sided medicine drawer! Cat Ashton clearly approves.

This is a self venting cat box I built. It does have a bathroom fan inline but, that turned out to be overkill. I tapped into the vent stack for the tub while I was remodeling the bathroom. Also did all the tile and everything else, really.

The box emits no smell, the hallway down one side traps loose liter before the cats jump out and keeps the dog from getting treats. It was a blast to make.