The ancient structure was located by divers during an excavation conducted by the Van Yüzüncü Yıl University this week, and is thought to have belonged to the Urartu civilisation during the Iron Age.
Footage has emerged of divers exploring the remarkably preserved ruins, which consist of walls that still reach up to 13 feet high and stonework that spans a kilometre.
“It is a miracle to find this castle underwater,” Chief diver Tahsin Ceylan told the Hürriyet Daily News, adding that archaeologists would be descending to the site in order to further assess its history.
According to National Geographic, the water level of Lake Van – a soda lake which stretches across 1449 square miles, the biggest in Turkey – was hundreds of metres lower during the Urartian occupation, which would explain its drowned state today.
Experts had already been investigating Lake Van for nearly a decade in search of its hidden treasures before stumbling across the fortress.
Last year they discovered a 2km stretch of stalagmites rising from the depths which they dubbed the “underwater fairy chimneys”.
The earliest mentions of Urartu date back to Assyrians in the early 13th Century BC, and by the 9th Century BC the nation was thriving, occupying a 200,000 square mile portion of the Middle East.
After a gradual decline in power that stemmed from a number of lost battles, Urartu was conquered by the Medes in the 6th Century BC, later to be succeeded by the Armenians.
Urartian remnants were first rediscovered by French scholars in the late 1820s, and excavations have been ongoing on and off since then.
Scatters of Urartian ruins can be visited in the surrounding areas of Lake Van in Turkey, as well as Armenia and Iran to this day.
If you want to read about another discovery in present day discovery then why not check out my post on the Vulture Stone.