In the winter of 479 B.C., a tsunami was the savior of Potidaea, drowning hundreds of Persian invaders as they lay siege to the ancient Greek village. New geological evidence suggests that the region may still be vulnerable to tsunami events, according to Klaus Reicherter of Aachen University in Germany and his colleagues. The Greek historian Herodotus described the strange retreat of the tide and massive waves at Potidaea, making his account the first description of a historical tsunami. Reicherter and colleagues have added to the story by sampling sediments on the Possidi peninsula in northern Greece where Potidaea (and...