Divers working in Egypt’s Abu Qir Bay have spent more than two decades gradually mapping the remains of Thonis-Heracleion, a major ancient port city that slipped beneath the Mediterranean more than a thousand years ago. Once one of Egypt’s principal gateways for trade with the Greek world, the city sank gradually rather than vanishing in a single catastrophe, leaving temples, statues, and dozens of shipwrecks preserved in the silt off the coast near Alexandria. Each diving season has added new detail to a site that took French underwater archaeologists years just to locate.
A Port City Egypt Thought Was Two Separate Places
For centuries, historians treated Thonis and Heracleion as two different cities, since ancient Egyptian sources referred to the port by its Egyptian name, Thonis, while Greek writers described a place called Heracleion. Both names appeared often enough in ancient texts that no one seriously questioned whether they might describe the same location until archaeologists finally found physical evidence underwater.
That changed when underwater excavations led by French archaeologist Franck Goddio and Egypt’s Supreme Council of Antiquities located the submerged remains of Thonis-Heracleion in Abu Qir Bay in the year 2000 and recovered a stone stela inscribed with both names applied to the same city, settling a question that had lingered since antiquity.
How the City Ended Up Underwater
Researchers studying the site attribute Thonis-Heracleion’s disappearance to a combination of gradual processes rather than a single dramatic event: slowly rising sea levels, soil liquefaction in the soft, water-saturated clay the city was built on, and gradual subsidence of the land itself all worked together over centuries. Some structures appear to have collapsed abruptly, possibly during a localized earthquake or tsunami, while much of the wider city sank more slowly as the ground beneath it gave way, a process that left buildings and monuments largely intact rather than reduced to rubble.
That combination of slow sinking punctuated by sudden localized collapse is why so much of the site survived in recognizable form instead of being scattered or destroyed. Buildings that settled gradually into softening clay tended to stay upright and largely intact even as they sank, while the sediment that eventually buried them helped protect statues, pottery, and other artifacts from the currents and marine life that typically break down exposed material on the open seafloor over centuries.
The Temple and Statues Divers Have Mapped
At the heart of the submerged city, divers located the remains of a temple dedicated to Amun-Gereb, the supreme god of the Egyptians in that region during the period the city flourished. Around the temple, the excavation team recovered colossal statues, including monumental figures depicting a pharaoh and his queen each standing more than sixteen feet tall, along with a red granite sphinx believed to represent a Ptolemaic-era pharaoh, all of it preserved by the sediment that eventually covered the site.
Sunken Ships and a Harbor Frozen in Place
Beyond the temple precinct, the harbor area has produced one of the largest concentrations of ancient shipwrecks found anywhere in the Mediterranean, with more than 60 vessels identified so far, many of them sunk deliberately as part of ancient religious ceremonies rather than lost in storms or accidents. Divers have also recovered close to 700 ancient anchors from the harbor, along with gold coins and finely detailed bronze and stone artifacts, all consistent with a working commercial port that handled substantial trade traffic between Egypt and the wider Mediterranean world before it sank.
The sheer density of wrecks and anchors packed into a relatively small stretch of harbor has helped archaeologists reconstruct how the port actually operated, from where larger seagoing vessels would have anchored offshore to the narrower channels smaller boats likely used to move goods closer to the temple district. Because so much of the harbor floor was buried quickly by shifting sediment rather than scavenged or disturbed by later builders, the layout has stayed close enough to its original state that researchers can trace individual mooring points rather than working from scattered, disconnected fragments.
What Continued Diving Seasons Keep Adding
Excavation of Thonis-Heracleion is still active, with the team returning for additional diving seasons that continue to expand the mapped area of the ancient port and refine the timeline for when different parts of the city went underwater. Each new season has tended to add fresh artifacts and structural detail rather than close out the site, and archaeologists involved in the project have said large sections of the ancient harbor and surrounding settlement remain unexcavated beneath the bay’s sediment, suggesting the full extent of the city is still not completely known even after more than twenty years of work.
Work at the site is slow by necessity, since visibility in Abu Qir Bay is often limited and every section of seafloor has to be surveyed, mapped, and partially excavated by hand before anything can be safely lifted or documented in place. That pace means Thonis-Heracleion has effectively become a long-running excavation rather than a single dig with a defined end date, with each diving season treated as one more layer added to a map that archaeologists expect to keep revising for years to come.
This article was produced with the assistance of AI and reviewed by Morning Overview editors.
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