A tunnel, presumed to have been built during the 15th century, was discovered under the Rumeli Fortress in the Sarıyer district of Türkiye’s Istanbul during the ongoing restoration works. According to the first examinations, the tunnel was used as a waterway line and drainage channel, and it received restoration until the 19th century.
The Rumeli Fortress was built in 1452, shortly before the conquest of Istanbul on 1453, to improve security on the Bosphorus and was used as gunpowder mill, ammunition depot, and state prison afterwards.