In the centre of the oasis is the old kasbah or citadel.
The kasbah forms the apex of a triangle of which the quays form the base.
The city consists of two parts; the modern French town, built on the level ground by the seashore, and the ancient city of the deys, which climbs the steep hill behind the modern town and is crowned by the kasbah or citadel, 400 ft.
They often end in a cul-de-sac. The principal street is the rue de la Kasbah, which leads up to the citadel by 497 steps.
The public buildings of chief interest are the kasbah, the government offices (formerly the British consulate), the palaces of the governor-general and the archbishop - all these are fine Moorish houses; the "Grand" and the "New" Mosques, the Roman Catholic cathedral of St Philippe, the church of the Holy Trinity (Church of England), and the Bibliotheque Nationale d'Alger - a Turkish palace built in 1799-1800.