Algiers ( ; ; ; , ) is the capital and largest city of Algeria. The city's population at the 2008 census was 2,988,145 and in 2020 was estimated to be around 4,500,000. Algiers is located on the Mediterranean Sea and in the north-central portion of Algeria. Algiers is situated on the west side of a bay of the Mediterranean Sea. The modern part of the city is built on the level ground by the seashore; the old part, the ancient city of the deys, climbs the steep hill behind the modern town and is crowned by the Casbah or citadel (a UNESCO World Heritage Site), above the sea. The casbah and the two quays form a triangle. Names The city's name is derived via French and Catalan from the Arabic name al-Jazāʾir (), "The Islands". This name refers to the four former islands which lay off the city's coast before becoming part of the mainland in 1525. Al-Jazāʾir is itself a truncated form of the city's older name Jazaʾir Banī Mazghanna (), "The Islands of the Banu Mazghanna", used by early medieval geographers such as Muhammad al-Idrisi and Yaqut al-Hamawi. In classical antiquity, the ancient Greeks knew the town as Ikósion (), which was Latinized as Icosium under Roman rule. The Greeks explained the name as coming from their word for "twenty" (, eíkosi), supposedly because it had been founded by 20 companions of Hercules when he visited the Atlas Mountains during his labors. Algiers is also known as el-Behdja (, "The Joyous") or "Algiers the White" () for its whitewashed buildings, seen rising from the sea. History Early history The city's earliest history was as a small port in Carthage where Phoenicians were trading with other Mediterraneans. After the Punic Wars, the Roman Republic eventually took over administration of the town, which they called Icosium. Its ruins now form part of the modern city's marine quarter, with the Rue de la Marine following a former Roman road. Roman cemeteries existed near '[Bab-el-Oued]] and Bab Azoun. The city was given Latin rights by the emperor Vespasian. The bishops of Icosium are mentioned as late as the 5th century, but the ancient town fell into obscurity during the Muslim conquest of the Maghreb. The present city was founded in 944 by Buluggin ibn Ziri, the founder of the Berber Zirid dynasty. He had built his own house and a Sanhaja