Heracleion, also known as Thonis and sometimes called Thonis-Heracleion, was an ancient Egyptian port city located near the Canopic Mouth of the Nile, about 32 km (20 mi) northeast of Alexandria on the Mediterranean Sea. Over time, the city became flooded, and its remains are now found in Abu Qir Bay, which is approximately 7 km (4.3 mi) from the coast and about 5.8 m (19 ft) underwater, near Abukir. The temple of Neith of Sais was located in Thonis. A stone tablet discovered at the site shows that the city was known by both its Egyptian and Greek names during its later years.

Thonis dates back to as early as the 12th century BC and is mentioned by ancient Greek historians. Its significance increased especially during the later years of the pharaohs.

History

Thonis was originally built on several islands in the Nile Delta. The city was centered around a large temple and had canals, harbors, and anchorages. Wharves, temples, and tall buildings were connected by ferries, bridges, and floating platforms. Thonis was a major trading port and became Egypt’s main port for international trade and tax collection during the Late Period. It had a sister city called Naucratis, located 72 km (45 mi) farther up the Nile. Goods were moved inland through Naucratis or sent via the Western Lake and a water channel to the nearby town of Canopus for further transport.

Thonis had a large temple dedicated to Khonsu, the son of Amun, who was known to the Greeks as Herakles. Later, worship of Amun became more important. Between the sixth and fourth centuries BC, when the city thrived, a major temple to Amun-Gereb, the most important Egyptian god at the time, stood in the city’s center. King Nectanebo I added many features to this temple in the fourth century BC. Temples in Heracleion dedicated to Osiris and other gods were known for miraculous healing and drew visitors from far away. Archaeologists have found evidence that the "Mysteries of Osiris" were celebrated in Thonis-Heracleion every year during the month of Khoiak. During this event, the god’s ceremonial boat was carried in a procession from the temple of Amun in the city to his shrine in Canopus.

Archaeological discoveries from 2023 suggest that Greeks, who were already allowed to trade in the city, began living there as early as the Twenty-sixth Dynasty of Egypt. Greek soldiers may have also been hired to protect the city.

In the second century BC, Alexandria became Egypt’s main port, replacing Thonis-Heracleion. The city’s importance declined as Alexandria grew, which was about 15 miles southwest. Around the same time, a major natural disaster—possibly a tsunami, earthquake, or both—caused serious damage to the city. However, Thonis-Heracleion was not completely abandoned until it sank entirely under the sea by the eighth century AD.

Over time, the city weakened due to earthquakes, tsunamis, and rising sea levels. Around 101 BC, after a severe flood, the ground on which the central island of Heracleion stood turned to liquid, a process called soil liquefaction. Earthquakes and tidal waves were recorded by ancient historians during the city’s decline. The area near the southeastern part of the Mediterranean Sea is naturally prone to soil liquefaction. When the hard clay turned to liquid, buildings collapsed into the water. A few people remained in the city during the Roman era and the early Arab period, but by the end of the eighth century AD, the city had completely disappeared beneath the sea.

For about 1,200 years, Thonis-Heracleion remained undisturbed under the ocean floor. Layers of sand and debris covered the city’s remains, making accidental discovery unlikely. This helped preserve the city. Looters and others had little chance to damage the ruins.

Greek references and legends

Thonis-Heracleion is mentioned by several Greek historians from ancient times, including Strabo, Diodorus, and Herodotus. These references often appear in stories about famous Greek figures, such as Heracles and Paris, and describe the city as being located on the coast near the Nile.

Strabo wrote that long ago, the city of Thonis, named after its king, was located on a narrow strip of land between the Mediterranean Sea and a canal that led to the city of Schedia.

Diodorus mentioned Thonis in a story about Heracles. He described how the Nile River once flooded heavily in an area ruled by Prometheus. Because the water moved so quickly, the river was called the Aëtus, or "eagle," until Heracles stopped the flood and redirected the river to its original path. Diodorus claimed that the myth of Heracles killing the eagle that ate Prometheus’s liver originated from this event. He also stated that the city of Thonis was located where the Nile now flows into the Mediterranean Sea.

Herodotus wrote that Paris and Helen of Troy, fleeing from Menelaus, landed in an area of the Nile delta called the Canopic mouth. Some of Paris’s servants later ran to a nearby temple of Heracles on the coast and told the temple priests and Thonis, the guardian at the entrance to the Nile, about Paris taking Helen from Menelaus. Thonis then captured Paris and his ships, bringing him and Helen to Memphis to be judged by Proteus of Egypt. Another account suggested that Menelaus and Helen stayed in the area, welcomed by the noble Egyptian Thon and his wife, Polydamna.

The Greek poet Nicander, who lived in the second century BC, wrote that Menelaus’s navigator, Canopus, was bitten by a viper on the sands near Thonis.

Egyptian references

Until recently, the site was only known from a few written records and inscriptions. One of these mentions the site as an emporion, similar to Naukratis.

Heracleion is also mentioned in two inscribed stones from the Decree of Nectanebo I (one of which is called the "Stele of Naukratis"). These stones state that one tenth of the taxes on goods brought into the town of Thonis (Heracleion) were to be given to the ancient temple of Neith of Sais. The city is also mentioned in the Decree of Canopus, which honors Pharaoh Ptolemy III. This decree describes donations, sacrifices, and a procession on water.

Discovery and excavation process

Before the second stele was found in 2000, most historians thought Thonis and Heracleion were two different cities located on what is now the Egyptian mainland. The stele was discovered in the temple of Heracleion and included an order from Nectanebo I to place it in the city of Thonis, showing that the two cities were actually the same. The ruins underwater were found and studied by French underwater archaeologist Franck Goddio and his team from the IEASM, working with Egypt’s Ministry for Antiquities after a five-year search. Goddio’s team first looked at historical records to find the possible location of the site. Then, they used several advanced tools, such as a nuclear magnetic resonance magnetometer, multi-beam bathymetry, sidescan sonar, sub-bottom profiler, and satellite positioning systems, to map the area. These technologies helped the team locate and study the site. After mapping, the team began careful excavations. They used a grid system to record the exact positions of artifacts and created an excavation plan. Every artifact was labeled and noted for its location. A water dredge was used to uncover more items. The team included archaeologists, artists, and photographers to document their findings. Dives were scheduled for about a month to maximize their time at the site. They worked systematically to uncover parts of the site during their time there. Goddio’s team follows a rule to leave artifacts in place unless permission is given by officials to move them for conservation or preservation. When moving an artifact, the team placed it in a plastic bag and raised it to the surface in a basket. For large items, like statues, they used a crane from their ship, the Princess Duda, to lift the artifact carefully. Once on the ship, artifacts were cleaned and treated with a desalination process to protect them from dry air after being underwater for a long time.

Artifacts found at the site show the city was active from the sixth to the fourth century BC, with pottery and coins stopping around the end of the second century BC. Goddio’s team also found incomplete statues of the god Serapis and Queen Arsinoe II, who later became a king.

Maritime archaeologists now use 3D technologies more often because of improvements in sonar, laser, optical, and other tools that can create detailed 3D maps of land, coastal areas, seabeds, and under-seabed sediments. These tools help archaeologists scan sites and make accurate maps and images, which is especially helpful for underwater locations.

Archaeological finds

From 2009 to 2011, a baris, an ancient boat used on the Nile River, was found underwater near the city of Thonis-Heracleion. The boat’s design matched a description written by the historian Herodotus in 450 BC.

The rapid destruction of buildings and slow sinking of Thonis-Heracleion allowed archaeologists to study the underwater city with many remains. One important find was a stele, a stone tablet, near the temple of Amun-Gereb. The stele, made of black granodiorite, recorded a decree by King Nectanebo I that provided financial support to the temple. This stele confirmed the city’s name as Thonis, which helped archaeologists and historians learn that Thonis and Heracleion were the same city. Other discoveries included about seventy ships near the city, the largest collection of ancient ships ever found. These ships give archaeologists valuable information about how they were built and what materials were used. A statue of either Cleopatra II or Cleopatra III, wearing a tunic like the goddess Isis, was also found. A large, complete statue of the god Hapi, holding a tray of bread, was uncovered. Many gold coins, statues of gods, jewelry, ritual animal sarcophagi, and ceramic items were found at the site. Some ceramics were Greek, showing that many Greeks lived in Thonis-Heracleion. Research at the site continues, and only about 5% of the city has been explored so far.

In July 2019, a tholos (a small Greek temple), ancient granite columns, ships carrying treasure, and bronze coins from the time of Ptolemy II (third and fourth centuries BC) were found by IEASM, a team of Egyptian and European archaeologists led by Goddio.

In August 2021, IEASM announced the discovery of a rare Ptolemaic galley, a type of warship. The 25-meter (82-foot) long ship had classic construction methods, such as mortise and tenon joints, and Egyptian features like a flat bottom for moving through the Nile and Delta. The ship was buried under heavy materials from collapsed buildings. It was found near the Temple of Amun and remained hidden until discovered. The ship had a sail and oars and combined Greek and Egyptian building techniques. This discovery shows how Greeks and Egyptians worked together in shipbuilding. A tumulus, or mound, was also found, containing offerings like baskets of doum palm fruit, grape seeds from the early 4th century BC, Greek pottery with black and red designs, and a wooden sofa used for banquets. A high-quality gold amulet was also found. These items were likely stored in an underground room or buried after being offered, even though the city continued to exist after the 4th century. This discovery shows that Greek merchants and soldiers lived in Thonis-Heracleion.

On 19 September 2023, IEASM announced the discovery of a temple to the god Amun and a Greek sanctuary for the goddess Aphrodite in the ancient city of Thonis-Heracleion. Many ancient Egyptian and Greek artifacts, including Greek weapons, were found at the site.