The capital city, Cairo, is Africa's largest city and has been renowned for centuries as a center of learning, culture and commerce of Egypt. Egypt also hosts two major religious institutions. Al-Azhar University, the oldest Islamic institution for higher studies (founded around 970 CE) with its corresponding mosque Al-Azhar. The head of Al-Azhar is traditionally regarded as the supreme leader of Sunni Muslims all over the world. Egypt also has a strong Christian heritage as evidenced by the existence of the Coptic Orthodox Church headed by the Patriarch of Alexandria, which has a following of approx. 50 million Christians worldwide - one of the famous Coptic Orthodox Churches is Saint Takla Haimanot Church in Alexandria.