Divers have discovered a rare military vessel amid the sunken ruins of the ancient Egyptian city of Thônis-Heracleion.

Measuring over 80 feet long, the flat-bottomed ship had both oars and a large sail. While built in the classical Greek style, it also incorporates some Egyptian shipbuilding traditions. The vessel was likely sunk when the nearby Temple of Amun collapsed; the remains were discovered beneath 15 feet of clay and debris from the building.

Excavations from a joint French and Egyptian mission led by the European Institute for Underwater Archaeology (IEASM) have also uncovered a 4th-century Greek funerary area.

“This discovery beautifully illustrates the presence of the Greek merchants who lived in that city,” read a statement from the Egyptian Ministry of Antiquities, as reported by Reuters. “They built their own sanctuaries close to the huge temple of Amun. Those were destroyed, simultaneously and their remains are found mixed with those of the Egyptian temple.”

The Greek ship is one of only two known surviving vessels of its kind, underwater archaeologist Franck Goddio wrote on the antiquities ministry’s Facebook page. Archaeologists found a similar style of vessel from 235 B.C. called the Masala Ship, in Sicily in 1971.

Prior to the founding of Alexandria by Alexander the Great in the year 331, Thônis-Heracleion was the largest port city in Egypt, controlling the entrance to the country at the mouth of a western branch of the Nile River.

The city was destroyed by earthquakes and sunk beneath the waves of the Mediterranean in the 8th century. It was rediscovered by Goddio’s IEASM team between 1999 and 2001. It was known as Heracleion to the Greeks (the historian Herodotus wrote of it in the fifth century B.C.), but Egypt called it Thônis. A plaque discovered during excavations helped experts realize that the two were one and the same.

See more photos from excavations below.

Remains of an ancient military vessel discovered in the Mediterranean sunken city of Thonis-Heracleion off the coast of Egypt. Photo by the Egyptian Ministry of Antiquities.

Remains of an ancient military vessel discovered in the Mediterranean sunken city of Thonis-Heracleion off the coast of Egypt. Photo by the Egyptian Ministry of Antiquities.

An artifact discovered in the Mediterranean sunken city of Thonis-Heracleion off the coast of Egypt. Photo by the Egyptian Ministry of Antiquities.