Vents.

I have the worst behaved cats. The vet thinks it's because I left for college and abandoned them and now they're in a constant state of panic that I'll leave again, but I think they're just dicks. They're so bad that I have to lock them in the cellar every night, lest they tear my house to shreds. Recently one of my cats discovered a new entry (we've boarded off three already) to the cold air ducts and incase you haven't ever heard a fat cat pace around in your cold air ducts let me tell you it's a horrifying sound.

  

This was just a test shot to see if I could shoot inside the vent. I didn't even know she was in there until after. Horrifying.