Also known as the Fortress of Seven Towers, the Yedikule Fortress is located just over 3 miles southwest of Sultanahmet. It was first built as the Golden Gate during the reigns of Theodosius I and II in the 5th century. With enormous doors covered in gold, the gate had four towers and was the ceremonial entrance to the city for those arriving from Europe. After the conquest of Constantinople in 1453, Mehmet the Conqueror added three towers to the structure to transform it into a fortress, treasury and prison. The towers today are known as the Armory Tower, the Flag Tower, the Sultan Ahmet III Tower, the Dungeon Tower (also known as the Tower of Inscriptions), the Top Tower, the Tower of the Treasury and the Young Osman Tower, where Sultan Osman II died while imprisoned.
The Yedikule Fortress also marks the end of the remaining land walls surrounding Istanbul. If you’re feeling adventurous, it’s possible to walk all the way on or along the walls between the fortress and Ayvansaray, about 7 kilometers north on the Golden Horn.