Talk about killing two birds with one stone!
If you're a people-watcher, like me, you might find this interesting (Allan sent this to me last week). It's an art exhibit at the Tate Britain (London), except it's also a functioning toilet situated on the street next to the museum. It would be strange actually using it, even though you know perfectly well people can't see in. I mean, imagine: doing your business, watching people walk by totally unaware that a) you're watching them, and b) you've got your trousers down.
Here's the full article.
I saw a German short film a couple of years ago that took place in Berliner Platz, about a sculpture artist who won a design contest to put an art piece in the middle of the plaza -- the busiest shopping district in probably all of Germany (somebody please correct me if I'm wrong). She then designed a one-way mirror cube as a stunt... a place where she and her boyfriend could fool around while people walked by, because they liked to be naughty in public places. Ah, you can always count on the Germans to take things one step further... the artist of the exhibit toilet, however, is Italian.