Nothing lasts forever. Just ask Ozymandias, or Nate Fisher. Only the wind inhabits the cliff dwellings at Mesa Verde in Colorado, birds and vines the pyramids of the Maya. Sand and silence have swallowed the clamors of frankincense traders and camels in the old desert center of Ubar. Troy was buried for centuries before it was uncovered. Parts of the Great Library of Alexandria, center of learning in the ancient world, might be sleeping with the fishes, off Egypt's coast in the Mediterranean. "Cities rise and fall depending on what made them go in the first place," said Peirce Lewis,...