It was built by Sultan Qaytbay (1468-1496 AD) on the ruins of the old Alexandria lighthouse. This castle is considered one of the most beautiful Islamic war castles in the Mediterranean basin. It was built to repel a possible invasion from the Ottoman Turks. It has an area of 17550 m2.
The design of the castle is octagonal and has a tower on the north side, which is square in shape, and each corner ends with a small round tower that ends at the top with a balcony and includes rooms. In the walls of the tower there are openings for shooting arrows. The historian Ibn Iyas mentions that there was a seat in the northern tower overlooking the sea in which those who sat could see the boats on A day’s march before entering the port.
Inside the citadel there is a mosque whose importance is due to the fact that it is architecturally one of the oldest known mosque in Alexandria, with an area of 30 m2.