Deep in Turkey’s biggest body of water, Lake Van, a secret fortress lay dormant for thousands of years, discovered recently by a team of university archaeologists following local rumors of a submerged structure.

Headed by Tahsin Ceylan, a group from Van Yüzüncü Yil University discovered this Iron Age marvel spanning over a half-mile deep below the surface, with walls stretching up to 13 feet above the bed of the lake.

What remains is a mixture of fallen stone piles and persistent structural surfaces dating back around 3,000 years to a time when the lake’s surface would have been hundreds of feet lower.

Overtime, the lake levels rose and the regional kingdom that existed as far back as the eight century BCE was to presumed to have been based in this area, and possibly this building compound.

In the wake of this discovery, researchers aim to revisit the site and begin to dig below the subsurface sediment in order to learn more about the kingdom and see just how deep this mystery really goes.