From the "smells like cat piss (and that's bad enough)" department:
This afternoon, it smelled like cat piss in my house. In the kitchen, the office, the dining room, but at worst in the floor/corridor, directly behind the entrance door. We looked everywhere, moved around stuff - you get the picture. Nothing.
I just couldn't imagine my Cäsar pi$$ing inside the house.
Then I noticed it also smelled like cat piss in front of the door. We sniffed at the door mat - nothing again.
Finally, finally we found it.
Since our walls are about one and a half foot thick, the cat flap is at the end of a small tunnel, and at the outside there's a frame around the hole. And exactly that frame had gotten peed on. I guess for marking purposes.
I don't know if it was Cäsar or another cat. I saw two different huuuge tomcats in our garden in the last days. There's some cat war going on on our property.
Bad as it is, I was relieved that Cäsar indeed did NOT pee inside the house.
I scrubbed the frame, and it's better now. Hope those damn cats will take their peeing contests elsewhere.