Heracleion (Ancient Greek: Ἡράκλειον Hērákleion), also called Thonis (Ancient Greek: Θῶνις Thônis; Ancient Egyptian: Tȝ-ḥn.t; Coptic: Ⲧϩⲱⲛⲓ Thōni) and sometimes named Thonis-Heracleion, was an ancient Egyptian port city near the Canopic Mouth of the Nile. It was about 32 km (20 mi) northeast of Alexandria on the Mediterranean Sea. Over time, the city was flooded, and its remains are now found in Abu Qir Bay, which is 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 there shows that the city was known by both its Egyptian and Greek names in its later years.

Thonis is believed to have been founded as early as the 12th century BC. It is mentioned by ancient Greek historians, and its importance increased especially during the final 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 connected by canals, which included many harbors and places where ships could tie up. Its wharves, temples, and tall buildings were linked by ferries, bridges, and floating platforms. Thonis was a major trading port, and by the Late Period, it became Egypt’s main port for international trade and tax collection. It had a sister city, Naucratis, located 72 km (45 mi) farther up the Nile. Goods were moved inland through Naucratis or transported via the Western Lake and a water channel to the nearby town of Canopus for further distribution.

Thonis had a large temple dedicated to Khonsu, the son of Amun, who was known to the Greeks as Herakles. Later, the worship of Amun became more important. During its peak between the sixth and fourth centuries BC, a large temple honoring Amun-Gereb, the most important Egyptian god at the time, stood in the center of the city. King Nectanebo I added many features to this temple in the fourth century BC. In Heracleion, temples dedicated to Osiris and other gods were famous for their healing powers and attracted visitors from far away. Archaeologists have found evidence that the "Mysteries of Osiris" were celebrated annually in 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 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 fifteen miles southwest of Thonis-Heracleion. Around the same time, a major natural disaster—possibly a tsunami, earthquake, or both—helped destroy the city. However, Thonis-Heracleion was not completely abandoned until it sank entirely underwater 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 was built turned to liquid, a process called soil liquefaction. Earthquakes and tidal waves were recorded by ancient writers during the city’s sinking. The area near the southeastern part of the Mediterranean Sea is naturally prone to liquefaction. The hard clay beneath the city turned into liquid, causing buildings to collapse 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 fully disappeared beneath the sea.

For 1,200 years, Thonis-Heracleion remained undisturbed under the ocean floor. Sand and debris covered the city’s remains, making accidental discovery unlikely. This helped preserve the city. Looters and others had no 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 involving famous Greek figures, such as Heracles and Paris, and describe the city as being located on the coast near the Nile.

Strabo wrote that the city of Thonis, named after its king, was once 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 where Prometheus was the governor. Because the river flowed so quickly, it 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.

Herodotus wrote that Paris and Helen of Troy, fleeing from Menelaus, landed in a part 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 watchman at the entrance to the Nile, about Paris taking Helen from Menelaus. Thonis then captured Paris and his ships and brought Paris and Helen to Memphis to be judged by Proteus of Egypt. Another account suggested that Menelaus and Helen had stayed in the region, hosted by the noble Egyptian Thon and his wife, Polydamna. The Greek poet Nicander, who lived in the second century BC, wrote that Menelaus’s helmsman, Canopus, was bitten by a viper on the sands of Thonis.

Egyptian references

Until recently, the site was known only from a few written records and inscriptions, one of which refers to it as an emporion, similar to Naukratis.

Heracleion is also mentioned in two stone tablets from the Decree of Nectanebo I (one of which is called the "Stele of Naukratis"). These tablets state that one-tenth of the taxes collected from imports passing through the town of Thonis (Heracleion) were to be given to the ancient temple of Neith in Sais. The city is also referenced in the Decree of Canopus, which honors Pharaoh Ptolemy III. This decree talks about gifts, offerings, and a boat parade.

Discovery and excavation process

Before the second stele was found in 2000, most historians thought Thonis and Heracleion were two different cities located on the Egyptian mainland. The stele was discovered at the temple of Heracleion and included an order from Nectanebo I to place it in the city of Thonis. This proved that Thonis and Heracleion were actually the same city. 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 studied historical texts to locate the site. They then used advanced technology, such as a nuclear magnetic resonance magnetometer, multi-beam bathymetry, sidescan sonar, sub-bottom profiler, and satellite positioning systems, to map the area. These tools helped them explore the site without disturbing it. Once mapped, the team began careful excavations. They used a grid system to record the exact positions of artifacts and created an excavation plan. Every item was labeled and documented. A water dredge was used to uncover more objects. The team included archaeologists, artists, and photographers to record the discoveries. They worked in a planned schedule for about a month, systematically uncovering parts of the site. Goddio’s team follows a rule to leave artifacts underwater unless officials approve moving them for conservation. When needed, artifacts were placed in plastic bags and raised in a basket. Large items, like statues, were lifted using a crane on their ship, the Princess Duda. After being brought to the ship, artifacts were cleaned and treated with desalination to protect them from dry air.

Artifacts from the site show the city was active from the 6th to 4th century BC, with pottery and coins found up to the end of the 2nd 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 technology more often because improvements in sonar, laser, and optical tools allow them to create detailed maps and images of underwater sites. These tools help archaeologists study submerged areas more accurately.

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 fast destruction of buildings and slow sinking of Thonis-Heracleion allowed archaeologists to study the city underwater, where many clues remain. One important find was a stele, a stone slab, near the temple of Amun-Gereb. The stele has a decree written by King Nectanebo I, which provided money for the temple. The stele also confirmed the city’s name as Thonis, showing that Thonis and Heracleion were the same city. This discovery changed earlier beliefs that they were separate cities. Other finds include about seventy ships near the city, the largest group of ancient ships ever found. These ships help archaeologists study how they were built and what materials were used. A statue of either Cleopatra II or Cleopatra III wearing the clothing of the goddess Isis was also found. A large, complete statue of the god Hapi, holding four loaves of bread, was discovered. Many gold coins, statues of gods, jewelry, ritual animal coffins, and pottery were uncovered. Some pottery was Greek, showing that many Greeks lived in the city. Research 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 warship 25 meters (82 feet) long. The ship had classic Greek construction methods, like mortise and tenon joints, and Egyptian features, such as a flat bottom for moving through the Nile. The ship was buried under heavy stones from buildings that collapsed during the city’s destruction. It was found near the Temple of Amun and had been trapped on the ocean floor until its discovery. The ship had a sail and oars and combined Greek and Egyptian building styles. This discovery shows how Greeks and Egyptians worked together to build ships in the city. A tumulus, a burial mound, was also found with offerings like baskets of doum palm fruit, grape seeds from the early 4th century BC, Greek pottery, and a wooden sofa used for banquets. A high-quality gold amulet was also discovered. These items were likely kept in an underground room or buried after being offered, even though the city continued to exist after the 4th century. This shows that Greek merchants and soldiers lived in the city.

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