It was constructed by Genoese as main tower of city walls surrounding Galata. Galata Tower was called Tower of Christ by the Genoese in 1348 and The Great Tower by the Byzantines.It was repaired many times after conquering of Istanbul. Galata Tower controlled the northern end of the sea chain that closed the entrance to Halic.
Used as a jail
The Tower was damaged during the earthquake in 16th century and it was restored. During the reign of Süleyman the Magnificent Galata Tower was used as a jail. After fire in 1830's, Sultan Mahmut added two more floors to the Galata Tower and covered the top with cloth in the shape of a conical hat.
It was used as dungeon for a period and later it was used as observatory. Now there is a restaurant at the top of tower. And this makes the tower as the best tower where dinner is served inside it.