Algiers (ælˈdʒɪərz ; al-Jazāʾir; Alger, alʒe) 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 in the north-central part of Algeria.
Algiers is situated on the west side of the Bay of Algiers, in 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.
The city's name is derived via French and Catalan Alger from the Arabic name al-Jazāʾir (الجزائر), "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 (جزائر بني مزغانة), "islands of Banu Mazghanna", used by early medieval geographers such as Muhammad al-Idrisi and Yaqut al-Hamawi. The name was given by Buluggin ibn Ziri after he established the city on the ruins of the Phoenician city of Icosium in 950. During Ottoman rule, the name of the capital, al-Jazā'ir, was extended over the entire country, giving it the English name Algeria derived from the French name Algérie.
In classical antiquity, the ancient Greeks knew the town as Ikósion (Ἰκόσιον), which was Latinized as Icosium under Roman rule. The Greeks explained the name as coming from their word for "twenty" (εἴκοσι, 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 (البهجة, "The Joyous") or "Algiers the White" (Alger la Blanche) for its whitewashed buildings.
Icosium
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.