THE archeologists could barely hide their excitement. Beneath the main square of Ecija, a small town in southern Spain, they had unearthed an astounding treasure trove of Roman history. They discovered a well-preserved Roman forum, bath house, gymnasium and temple as well as dozens of private homes and hundreds of mosaics and statues — one of them considered to be among the finest found. But now the bulldozers have moved in. The last vestiges of the lost city known as Colonia Augusta Firma Astigi — one of the great cities of the Roman world — have been destroyed to build...