A view straight down beneath the sidewalk on 7th St. NW near the Gallery Place Metro Chinatown entrance. The sidewalks in downtown DC feature grates like this all over the place. I've always just assumed they are metro maintenance access points and/or have something to do w/ventilation for the metro. Usually if you look down into them you don't see much but trash; this one seemed to be lit up for some reason.

You're fascinated, I know.