88 Princeton elms........

Main Arteries and Streets -- From the Capitol, North Capitol Street and South Capitol Street run north and south, respectively. East Capitol Street divides the city north and south. The area west of the Capitol is not a street at all, but the National Mall, which is bounded on the north by Constitution Avenue and on the south by Independence Avenue.

The primary artery of Washington is Pennsylvania Avenue, which is the scene of parades, inaugurations, and other splashy events. Pennsylvania runs northwest in a direct line between the Capitol and the White House -- if it weren't for the Treasury Building, the president would have a clear view of the Capitol -- before continuing on a northwest angle to Georgetown, where it becomes M Street.

Pennsylvania Avenue in front of the White House -- between 15th and 17th streets NW -- remains closed to cars for security reasons but has been remade into an attractive pedestrian plaza, lined with 88 Princeton American Elm trees.