Pavement* fascinates me. Not the pavement itself, but the character that develops on it over time. One of these days I'm going to go out into the city for a day and just photograph the ground.
*I may be using the term pavement wrong. If you're a pavement expert, please forgive my ignorance. When I say pavement, I mean concrete, cement, asphalt, or whatever it is I happen to be seeing at that moment.