I've always been fascinated by the reflective quality of water. With clear, shallow pools and puddles, you can see not only right through to the bottom, but from the right perspective you can also see what the water reflects. If you really look, you see something entirely different (Just like a Magic Eye book. I loved those books! Did you?).
Walking around NYC after a day of rain is absolutely fascinating, because I see the city from a different perspective as I navigate through the puddles. In this case, looking down helps me to look up.