Over the centuries the belief lingered on that here had been a great, wealthy, powerful commercial city that dominated the mouth of the Po and the shores of the Adriatic, a city of luxury and splendor, a kind of ancestor and predecessor of Venice, founded more than a thousand years later. Classical scholars also knew about Spina, for ancient literary sources indicated that there must once have existed a thriving maritime trading settlement of great economic importance, until the Celtic invasion of the Po valley destroyed it... The final key to its ultimate discovery came from aerial photography. Some...