The city of Heracleion was swallowed by the Mediterranean Sea off the coast of Egypt nearly 1,200 years ago. It was one of the most important trade centers in the Mediterranean before it sank more than a millennium ago. For centuries, the existence of Heracleion was believed to be a myth, much like the city of Atlantis is viewed today. But in 2000, the underwater archaeologist Franck Goddio finally found the sunken city after extensive underwater research in today’s Aboukir Bay...