The U.S. Capitol's Visitor Center is the quintessential public-works project. It began as a modest proposal in 1994: Build an underground area where tourists could get out of the elements while they wait in line to tour the Capitol. From its $70 million beginnings, however, it mushroomed into a three-story, 580,000-square-foot monstrosity that is three-quarters the size of the Capitol itself. Ostentatious only begins to describe the center, which has been dubbed "Congress' tribute to itself." It includes a TV studio where members may record messages for the folks back home, two theaters, an auditorium and an exhibition hall, and...