We admired the quality of the graffitti in the European cities. It's everywhere and on everything, just like in the States, but it appears a little more artistic. Not all of it nasty gang slogans, some of it was quite good artistically speaking.
Rome smells like urine. Very strongly of urine. I didn't notice it elsewhere, just Rome.
In France there was some minor trash alongside the road when we went for a walk from our "close-to-the-airport" hotel. It wasn't bad.