A cataclysm in the classical world
On a winter night in 373 BCE, the Greek city of Helike vanished. The ground shook violently, and a massive tsunami surged from the Gulf of Corinth, engulfing the city and a neighboring settlement, Boura. Ancient writers documented that just days before the disaster, animals, including snakes and weasels, fled from the coast toward the mountains. The catastrophe was so complete that all inhabitants perished, along with ten Spartan ships anchored in the harbor.
The cause of this event lies in geology. The Gulf of Corinth is one of Europe's most seismically active regions, a continental rift valley that is actively widening. The earthquake triggered a phenomenon called soil liquefaction, where the saturated soil beneath the city behaved like a liquid, causing the entire settlement to sink several meters. The subsequent tsunami buried what was left. For centuries, the submerged ruins were a tourist attraction for the Romans, who sailed over the site to view the city's sunken walls and a bronze statue of Poseidon. The Greek traveler Pausanias noted in the 2nd century CE that the walls were still visible, though corroded by saltwater. Over time, sediment from the nearby Selinous and Kerynites rivers completely buried the site, and its exact location was lost.
The search for a buried city
For decades, archaeologists believed the city's remains lay on the seabed of the Corinthian Gulf. Early search efforts, including sonar surveys of the seafloor in 1988, found evidence of seismic disturbances but no city. The breakthrough came when archaeologist Dora Katsonopoulou and physicist Steven Soter of the Helike Project re-evaluated ancient texts. They considered that the term poros, used by ancient writers to describe where the city lay, might mean "inland lagoon" rather than the open gulf.
This shift in thinking directed their search to the coastal plain. Using borehole drilling, the team analyzed sediment cores and found ceramic fragments, indicating a buried settlement. Finally, in 2001, excavations near the village of Rizomylos uncovered the ruins of Classical Helike, buried 3 meters deep under layers of clay and sand. The discovery was confirmed in 2012 when a "destruction layer" was found, containing cobblestones, roof tiles, and pottery from the 4th century BCE, consistent with the great earthquake. The city was not in the sea, but under it, in an ancient lagoon that had long since silted over.
The excavations revealed multiple cities. Below the Classical ruins, archaeologists found a well-preserved Early Bronze Age settlement from around 2400 BCE, complete with cobbled streets and large buildings. This suggests the site has been subject to repeated destruction by earthquakes over millennia. The anoxic, muddy environment of the lagoon preserved organic materials rarely found in other excavations, showing life in the ancient Greek world.