"Does Dubai really need the world's tallest building?" Petroski asks. "These things take great will, and you have to ask, Why are they being built?" One reason: Because they can be built by the nations that undertake them. Meanwhile, nations with a long history of superbuilding move on. The United States has skyscrapers and bridges galore. Now it's embarking on the world's most ambitious ecosystem restoration and the world's first long-term nuclear waste storage facility.