Aden (UK AY-duhn, US AH-den; Arabic: عدن ʻAdin/ʻAdan Yemeni pronunciation: [ˈʕæden, ˈʕædæn]) is a seaport city in Yemen, located by the eastern approach to the Red Sea (the Gulf of Aden), some 170 kilometres (110 mi) east of Bab-el-Mandeb. Its population is approximately 800,000 people. Aden's ancient, natural harbour lies in the crater of a dormant volcano which now forms a peninsula, joined to the mainland by a low isthmus. This harbour, Front Bay, was first used by the ancient Kingdom of Awsan between the 5th and 7th centuries BC. The modern harbour is on the other side of the peninsula. Aden gives its name to the Gulf of Aden.
Aden consists of a number of distinct sub-centres: Crater, the original port city; Ma'alla, the modern port; Tawahi, known as "Steamer Point" in the colonial period; and the resorts of Gold Mohur. Khormaksar, located on the isthmus that connects Aden proper with the mainland, includes the city's diplomatic missions, the main offices of Aden University, and Aden International Airport (the former British Royal Air Force station RAF Khormaksar), Yemen's second biggest airport. On the mainland are the sub-centres of Sheikh Othman, a former oasis area; Al-Mansura, a town planned by the British; and Madinat ash-Sha'b (formerly Madinat al-Itihad), the site designated as the capital of the South Arabian Federation and now home to a large power/desalinization facility and additional faculties of Aden University.