An airport in Amsterdam has an image of a fly in each of their men's room urinals because it is the "sweet spot" for less splashing, and men instinctively aim for the fly.
The idea is that there's a "sweet spot" which reduces splash as much as possible when peeing in a urinal. The airport decided that a good way to help keep their bathrooms clean was to reduce splash as much as possible, so they wanted people hitting this sweet spot as much as possible.
How do you get someone to pee in a certain spot? Maybe there are a lot of answers to that question, but this German airport decided to go with fake flies to drive user behavior.
Men instinctively aim for the flies. It's not clear why, but it seems to work and keeps the bathroom that much cleaner.
