The Yedikule Fortress (Castle of Seven Towers)
The first fortress behind the Golden Gate began being built during the reign of John I Tzimiskes and was completed under Manuel I Komnenos. That fort (Kastellion) had five towers, and was hence also named Pentapyrgion. It was destroyed after the first fall of the city to the Fourth Crusade, and rebuilt only in 1350 by John VI Kantakouzenos. The new fort featured five octagonal towers, and together with the two marble towers of the Golden Gate, seven in total, becoming known as the Eptapyrgion ("Seven Towers"). In 1391 however, John V Palaiologos was forced to raze the fort by Sultan Bayezid I, who otherwise threatened to blind his son Manuel, whom he held captive. Emperor John VIII Palaiologos attempted to rebuild it in 1434, but was thwarted by Sultan Murad II.