It’s grassy. It’s open. It’s blank space between monuments. At least one person’s asked you where it is, while standing on it. You’ve been there with out of town visitors. Yes, it’s the National Mall. You think you know it inside and out. Well, unless you’ve got some strong anti-aging elixir that you’re about to make a fortune on, you’re not likely to know how it looked way back when the Washington Monument was just a stub. Or that, before Smithsonian Folklife, the Armory Square Hospital stood on its grounds. The paths used to be crazy loopy and there was a train terminal right where the National Gallery stands.  It’s hard to imagine a time when trains ran alongside the mall when there’s an interactive location based app designed around it now. It may seem modern but it was only designed in 1901, when the plan was drawn for the mall we all know and love.