Photo by Wikipedia user AgnosticPreachersKid. If you’ve ever made the walk from Nationals Stadium to Barracks Row for a drink after a game, or perhaps just live in the Navy Yard area – you’ve certainly noticed the building dubbed “Blue Castle” on the corner of 8th and M Streets SE. It’s a bit hard to miss, an old building painted various shades of blue. Now the home for two charter schools, the building used…