Gadir, now Cádiz, was in legend founded by Gadeirus, the twin brother of Atlas. It is also associated with Melkart-Herakles-Hercules and the temple of Hercules in Gades was visited by Hannibal, Caesar and others in the historical record.
"To his twin brother, who was born after him, and obtained as his lot the extremity of the island towards the Pillars of Heracles, facing the country now called the region of Gades, he gave the name which in the Hellenic language is Eumelus, but in the native tongue Gadeirus; and this may be the reason why the country was called Gades." Plato's Critias (113d–114a).
One of the theories about the location of Atlantis places it within the Lacus Ligustinus opposite Cádiz. This region has suffered many tsunamis even in historic times, the 1755 Lisbon tsunami being the most notable. There is geological evidence of much larger, much older tidal waves.
Any archeological remains would be deeply buried by mud in the marshes... but advances in ground penetrating radar, SAR, Lidar and other techniques mean that for the first time in history they could be found.
