Just to note, most of the underground stations on the Washington D.C. metro system are bare concrete. The way the stations are constructed, using a low barrier

Just to note, most of the underground stations on the Washington D.C. metro system are bare concrete. The way the stations are constructed, using a low barrier wall, discourages people from touching the main station walls. The low light kind of also helps hide some of the grime. But overall they're relatively clean. https://en.wikipedia.org/wiki/Washington_Metro https://en.wikipedia.org/wiki/Washington_Metro