In 969, the Fatimid empire ruled over Egypt after conquering Ifriqiya, and under the rule of its founder Jawhar Al Saqili, a new fortified city northeast of Fustat was established. It took four years to build the city, initially known as al-Manṣūriyyah, which was to serve as the new capital of the caliphate. During that time, the construction of the al-Azhar Mosque was commissioned by order of the Caliph, which developed into the third-oldest university in the world. Cairo would eventually become a centre of learning, with the library of Cairo containing hundreds of thousands of books. When Caliph al-Mu'izz li Din Allah arrived from the old Fatimid capital of Mahdia in Tunisia in 973, he gave the city its present name, ''Qāhirat al-Mu'izz'' ("The Vanquisher of al-Mu'izz").