Human history is rife with tales of lost civilizations, but unlike the legendary Atlantis or El Dorado, most "lost" cities didn't fall into the sea or disappear overnight. Historian Annalee Newitz travels to four famous "lost" cities—Catalhöyük in Turkey, Pompeii in Italy, Angkor Wat in Cambodia, and Cahokia in the United States—to explain how environmental, social, and economical factors could cause a massive civilization to fall from a teeming metropolis to forgotten ruins, and how our own urban centers could suffer the same fate.