These stairs don't look quite up to code, but they all look well loved. This photo collection features steps that have been indented and sculpted over time by the feet of people who walk them — slowly, imperceptibly, one footfall at a time, until the stone dips in the center like a hammock. All of these staircases look like works of art after many years of wear. There's something quietly moving about it: the cumulative weight of thousands of anonymous lives, pressed into marble and granite. I'm glad someone is out there photographing them in case they get replaced by new, boring stairs. Despite the trip hazard, these are my favorite kind. The collection includes steps from across the world — medieval European churches, ancient Asian landmarks, public monuments, tourist sites that see millions of visitors a year. Some of the most dramatically worn examples come from places where the same route has been walked daily for centuries, the stone gradually remembering every foot that ever crossed it.…