Over 20 hectares of Roman ruins discovered submerged off Tunisian coast
Neapolis (ZME Science)

On July 21, 365 AD the pearl-city of Alexandria, Egypt was devastated by a massive tsunami which was triggered by an earthquake off the coast of Greece. Though the ancients couldn't measure earthquakes at the time, contemporary scientists estimated from the historical records that the largest of the two tremors had a magnitude of 8.0.