In 1996, diver and archaeologist Franck Goddio raised from the waters of Abu Qir Bay, northeast of Alexandria, a colossal two-tonne pink granite bust. It was the first head of a Ptolemy ever found in situ in centuries. Beneath the Mediterranean, just a few meters below the surface, lies one of Antiquity's most fabulous cities. This SLICE Histoire documentary plunges into the turbid waters of Alexandria to find the ghosts of a sunken metropolis.

Historical map of Alexandria, Richard Pococke, 1743
Historical plan of Alexandria by Richard Pococke (1743), showing the layout of the ancient Ptolemaic city. (Credit: Richard Pococke, Public domain, Wikimedia Commons)

Alexandria, jewel of the Mediterranean

Founded in 331 BC by Alexander the Great on Egypt's northern coast, Alexandria became within decades the capital of the Hellenistic world. Under the Ptolemaic dynasty, it housed the greatest library of Antiquity, the Mouseion (ancestor of our universities), and the famous Lighthouse, one of the Seven Wonders of the Ancient World. At the height of its power in the 1st century BC, the city counted nearly a million inhabitants, making it one of the largest cities on earth.

The royal quarter -- the Brucheion -- spread across the northeast peninsula of the city, directly on the seafront. This sector housed the Ptolemaic palaces, royal gardens, the mausoleum of Alexander the Great, and the artificial island of Antirhodos, the sovereigns' summer residence. It is precisely this quarter that earthquakes and ground subsidence progressively caused to slide beneath the waters between the 4th and 8th centuries AD.

The catastrophe that swallowed a city

Alexandria's submersion was not a single spectacular event but a slow and inexorable process. Series of earthquakes -- including the catastrophic 365 AD quake that triggered a devastating tsunami across the eastern Mediterranean -- progressively caused the Nile delta to subside. The unstable ground on which the city was built, consisting of alluvial sediments, settled and sank over the centuries.

The result is visible today to anyone who dives in Abu Qir Bay or Alexandria's eastern harbor: at less than six meters depth, pink granite columns, sphinxes, colossal statues and building foundations spread over hectares of seabed. Visibility is often poor due to water turbidity, but discoveries made since the 1990s have totally transformed our understanding of this mythical city.

Statue of Hermes-Thoth, Ptolemaic period, found near Alexandria
Statue representing Hermes-Thoth (2nd century BC), in Greco-Egyptian style, found in the Alexandrian region's excavations. (Credit: Public domain, Wikimedia Commons)

Franck Goddio and the European Institute of Underwater Archaeology

In 1992, French archaeologist Franck Goddio, founder of the European Institute of Underwater Archaeology (IEASM), obtained the Egyptian government's authorization to excavate Alexandrian waters. Equipped with the most advanced technologies -- side-scan sonar, magnetometry, underwater GPS mapping -- his team began by drawing an exhaustive map of the seabed in the eastern harbor and Abu Qir Bay.

This preliminary cartographic work, which took several years, led to extraordinary discoveries. In the eastern harbor, Goddio identified the remains of the royal Brucheion quarter: palace foundations, quays, a partly paved avenue, and the island of Antirhodos with its docks and constructions. Hundreds of artifacts were raised: granite statues, sphinxes, columns, amphorae, coins, jewelry and numerous ceramic and glass objects.

The Lighthouse of Alexandria: a legend beneath the waves

One of underwater Alexandrian archaeology's most compelling questions concerns the Lighthouse, that colossal tower approximately 120 meters tall that guided ships into the harbor from the 3rd century BC. Damaged by earthquakes, it gradually collapsed between the 10th and 14th centuries. In the 14th century, Mamluk sultan Qaitbay used its materials to build a fortress -- Fort Qaitbay -- which still stands today at the lighthouse's presumed location.

In 1994, diver and historian Jean-Yves Empereur conducted the first underwater excavations around Fort Qaitbay. His team discovered dozens of colossal red granite blocks -- some weighing up to 70 tonnes -- along with sphinxes, statues, and obelisks. Though these elements were likely displaced from their original position by earthquakes and tsunamis, some fragments may belong to the Lighthouse itself or its ancillary structures.

Fragment of a statue of Cleopatra VII, Royal Ontario Museum
Statue fragment likely representing Cleopatra VII (1st century BC), Royal Ontario Museum, Toronto. (Credit: Royal Ontario Museum, CC BY-SA 3.0, Wikimedia Commons)

Cleopatra and the sunken royal quarters

Goddio's excavations in Abu Qir Bay have helped locate what may be the palace of Cleopatra VII, Egypt's last queen, who seduced Julius Caesar and Mark Antony before her death in 30 BC. Several large-scale structures have been identified on Antirhodos island and surrounding areas: marble-paved rooms, basins, columns and a monumental jetty.

Among the most remarkable objects raised in this area are statues of Egyptian deities in black granite, a limestone sphinx, marble architectural decorations and an abundance of luxury ceramics imported from Greece and Italy. These testimonies of a court life of extreme opulence confirm descriptions that ancient authors -- Strabo, Cassius Dio -- left us of the Ptolemies' incomparable splendor.

The challenges of underwater archaeology in Egypt

Excavating beneath Alexandrian waters is no small feat. Visibility is often reduced to a few dozen centimeters due to suspended sediments -- Nile silt and harbor discharge -- and intense maritime traffic complicates operations. Divers must work with underwater suction dredges to clear objects, protective nets to prevent artifacts from drifting in currents, and sophisticated lifting systems to raise blocks weighing several tonnes.

Object preservation also poses serious challenges. Organic materials -- wood, leather, fabric -- do not survive in the warm, turbid waters of the eastern Mediterranean, unlike northern wrecks. Metal artifacts are often corroded. Only stone, ceramics and glass survive well. Despite these constraints, Alexandrian excavations have produced over thirty years a wealth of discoveries that has allowed historians to rewrite the story of one of Antiquity's most important cities.