The ballpark for the Washington Nationals (the baseball team formerly known as the Montreal Expos) opened in the spring of 2008, and it’s the first LEED-certified professional sports facility. One of the things that earned Nationals Park this distinction is its pedestrian-friendly site, about a mile and a half south of the Capitol Building: it’s on the Anacostia riverfront, part of an effort to reclaim and redevelop a seedy industrial area, and it’s convenient to the Navy Yard Metro station. Most fans will likely pick up on the 6,300-square-foot green roof atop the hot-dog stand over by left field, and the observant ones will notice that their beer comes in cups made from biodegradable, corn-derived plastic. Less visible is the series of four cisterns beneath the park, designed to filter peanut shells and the chemicals used to maintain ball-field grass out of the runoff water before it reaches the long-abused river. Fans who bike to the park will appreciate the free valet bike-parking service.