Aden (/ˈɑːdɛn/ AH-den; Arabic: عدن ʻAdan) is a seaport city in Yemen, located by the eastern approach to the Red Sea (the Gulf of Aden), some 170 kilometres east of Bab-el-Mandeb. Its population is approximately a million 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 BCE. The modern harbour is on the other side of the peninsula.