Cairo has the oldest and largest film and music industries in the Arab world, as well as the world's second-oldest institution of higher learning, Al-Azhar University. Many international media, businesses, and organizations have regional headquarters in the city; the Arab League has had its headquarters in Cairo for most of its existence.
With a population of over 9 million spread over 3,085 square kilometers (1,191 sq mi), Cairo is by far the largest city in Egypt. An additional 9.5 million inhabitants live in close proximity to the city. Cairo, like many other megacities, suffers from high levels of pollution and traffic. Cairo's metro, one of two in Africa (the other being in Algiers, Algeria), ranks among the fifteen busiest in the world, with over 1 billion annual passenger rides. The economy of Cairo was ranked first in the Middle East in 2005, and 43rd globally on Foreign Policy's 2010 Global Cities Index.
Egyptians often refer to Cairo as Maṣr (IPA: ; Egyptian Arabic: مَصر), the Egyptian Arabic name for Egypt itself, emphasizing the city's importance for the country. Its official name al-Qāhirah (Arabic: القاهرة) means "the Vanquisher" or "the Conqueror", supposedly due to the fact that the planet Mars, an-Najm al-Qāhir (Arabic: النجم القاهر, "the Conquering Star"), was rising at the time when the city was founded, possibly also in reference to the much awaited arrival of the Fatimid Caliph Al-Mu'izz who reached Cairo in 973 from Mahdia, the old Fatimid capital. The location of the ancient city is the suburb of Ain Shams (Arabic: عين شمس, "Eye of the Sun"). The ancient Egyptian name for the area is thought to be Khere-Ohe, "The Place of Combat", supposedly in reference to a mythical battle that took place between Seth and Horus. Sometimes the city is informally referred to as Kayro by people from Alexandria (IPA: ; Egyptian Arabic: كايرو).
The area around present-day Cairo, especially Memphis, had long been a focal point of Ancient Egypt due to its strategic location just upstream from the Nile Delta. However, the origins of the modern city are generally traced back to a series of settlements in the first millennium. Around the turn of the 4th century, as Memphis was continuing to decline in importance, the Romans established a fortress town along the east bank of the Nile. This fortress, known as Babylon, was the nucleus of the Roman and then the Byzantine city and is the oldest structure in the city today. It is also situated at the nucleus of the Coptic Orthodox community, which separated from the Roman and Byzantine churches in the late 4th century. Many of Cairo's oldest Coptic churches, including the Hanging Church, are located along the fortress walls in a section of the city known as Coptic Cairo.
Following the Muslim conquest in 640 AD, the conqueror Amr ibn As settled to the north of the Babylon in an area that became known as al-Fustat. Originally a tented camp (Fustat signifies "City of Tents") Fustat became a permanent settlement and the first capital of Islamic Egypt.