As you approach it, this 11th-century oasis town looks somewhat like San Francisco: It's built on hills, its mosque (constructed in the Sudanese style) is reminiscent of Coit Tower, there are few trees on the streets, and the buildings are painted in lovely pastel shades.
A fairly large city on the northern edge of the desert, Ghardaia provides many of the comforts lacking in other oases (there are even ice cream and pastry shops). Be sure to visit the wonderful, exotic market—on the streets leading to it you'll pass a hammam as well as shops and stalls selling used genie lamps (no harm in giving one a rub) and carpets.
300 mi/480 km south of Algiers.