It was only a legend. Appearing in a few rare inscriptions and ancient texts, the city of Thonis-Heracleion was not something anyone expected to find, and no one was looking for it.
So it was something of a shock when French archaeologist Franck Goddio, looking for 18th-century French warships, saw a colossal face emerge from the watery shadows. Goddio had stumbled upon Thonis-Heracleion completely submerged 6.5 kilometres off Alexandria's coastline. Among the underwater ruins were 64 ships, 700 anchors, a treasure trove of gold coins, statues standing at 16 feet, and most notably the remains of a massive temple to the god Amun-Gereb, and the tiny sarcophagi for the animals that were brought there as offerings.
The ruins and artifacts made from granite and diorite are remarkably preserved, and give a glimpse into what was, 2300 years ago, one of the great port cities of the world. The harbor of Thonis-Heracleion (the Egyptian and Greek names of the city) controlled all the trade into Egypt.
Built around its grand temple, the city was criss-crossed with a network of canals, a kind of ancient Egyptian Venice, and its islands were home to small sanctuaries and homes. Once a grand city, today its history is largely obscured and no one is quite sure how it ended up entirely underwater.