Egypt, officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia by a land bridge formed by the Sinai Peninsula. Egypt is a Mediterranean country bordered by the Gaza Strip (Palestine) and Israel to the northeast, the Gulf of Aqaba and the Red Sea to the east, Sudan to the south, and Libya to the west. Egypt has one of the longest histories of any country. The country continues to face challenges, from political unrest, including the recent 2011 revolution and its aftermath, to terrorism and economic underdevelopment. Egypt's current government is a semi-presidential republic which has been described by a number of watchdogs as authoritarian. Islam is the official religion of Egypt and Arabic is its official language. With over 100 million inhabitants, Egypt is the most populous country in North Africa, the Middle East, and the Arab world.  The great majority of its people live near the banks of the Nile River. About half of Egypt's residents live in urban areas, with most spread across the densely populated centres of greater Cairo, Alexandria and other major cities in the Nile Delta.