The new U.S. embassy in Baghdad is shaping up to be the largest and most lavish embassy in the world. Tucked inside the heavily fortified Green Zone, the $600-million compound will include grocery stores, a movie theater, tennis courts and a club for social gatherings. In The Mega Bunker of Baghdad," Vanity Fair reporter William Langewiesche describes the compound - and argues that it's not being built for diplomacy.