Djémila bears eloquent exceptional testimony to the Roman civilization and constitutes an outstanding example, with its forum, temples, basilicas, triumphal arches and houses, of an architectural ensemble representative of Roman culture. It is also is an interesting example of Roman town planning adapted to a mountain location.

The Roman colony of Cuicul was probably founded on the present site of Djémila, during the brief reign of Nerva (AD 96-98). The early city, whose name is of Berber origin, occupies a remarkable defensive position on a rocky spur which spreads at an altitude of 900 m, between two mountain streams, Wadi Guergour and Wadi Betame.

The classic formula of Roman urban planning was adapted to the physical constraints of the site: at both ends of the cardo maximus, the backbone of the city, are two gates. In the centre is the forum, an enclosed square surrounded by buildings essential to the functioning of civil life: the capitolium to the north, the curia to the east, a civil basilica (Basilica Julia) to the west. Aristocratic dwellings set with rich mosaics from which they take their contemporary names (the House of Amphitrite, the House of Europa, etc.) multiplied during the course of the 2nd century in this central quarter, where the Temple of Venus Genetrix and the macellum (covered market) are also located. However, this cramped defensive situation, hemmed in by walls, hindered the development of the city.

In the mid-2nd century the city therefore expanded to the south, where a new quarter, rich in both public buildings and private dwellings, was established. Here were built the Arch of Caracalla, the temple of the family of Severus, a new forum, a theatre (already completed under Antoninus Pius), and, further along, baths constructed in the reign of Commodus. Among the buildings of the classical period the Basilica Vestiaria (cloth market) and a fountain that is a small-scale replica of the Meta Sudans in Rome are noteworthy. Christianity was implanted in the southern quarter at an early date. The remains of a group of episcopal buildings have been located there: two basilicas, a baptistry, a chapel and several houses, the residence of the bishop and the priest.

The Vandals were in Djémila for only a short time; the city was retaken by the Byzantines in 553. Excavations did not begin on the abandoned site, which is one of the world's most beautiful Roman ruins, until 1909.