Local rumors and stories about a lost city spurred divers to explore the bottom of Turkey’s largest lake, Lake Van. And they found some very real evidence of a former civilization in the form of an ancient fortress.

The fortress is estimated to be 3,000 years old and probably derived from the ancient Empire of Urartu, an Iron Age kingdom centered on Lake Van in the Armenian Highlands. The length of the fortress is about 1,000 meters, while the height of the walls varies between approximately 3 to 3.5 meters high.