Built from 1570 to 1573 by Ulj Ali, the military ruler of Algiers, and named for a military victory over the Spanish, this fortress overlooks the medina from the north. All that remains are two long wall sections and one citadel. The views across the town, over the modern cement amphitheatre, are stupendous.
Note the entrance is on the northern side of the fort – you have to walk the long way around if coming from the medina.