Union Station, Washington, D.C. A little history:
At the time it was built, the Station covered more ground than any other building in the United States and was the largest train station in the world. The Station sits on the edge of an area once known as "Swampoodle," an infamous shantytown located on the sewery remnants of Timber Creek. The total area occupied by the Station and the terminal zone was originally about 200 acres and included 75 miles of tracks. In fact, if put on its side, the Washington Monument could lay within the confines of the Station's concourse.
Of course the history page doesn't mention it, but this great hall is lined around the top with statues of Roman Soldiers, all of whom were retrofitted w/"modesty shields" to hide their goods. Apparently the shields don't cover everything if you look in the right place.