Arlington National Cemetery goes back to the Revolution. Four million people visit it each year. A few years ago, there was a scandal involving unmarked or mismarked graves, and urns unearthed and dumped in a dirt pile. That's been resolved and digitized records now allow visitors to look up grave sites on-line. Arlington's just completed an enormous new columbarium, two football fields long, that would add sites for 27,000 more interments, but it will run out of space for burials in 2025. Christian Davenport is editor on the Metro Desk at the Washington Post.