In brief
The urban model adjusts to the specific location.
Useful to know
Djémila, the ancient Cuicul in present-day Algeria, shows how Roman town planning adapted to a mountainous environment. The remains include forums, temples, basilicas, triumphal arches, and dwellings. [1]
To understand the object, keep track of the relationship between the public spaces and the terrain. It is not enough to recognize a column or an arch: it is more important how urban functions are arranged under limited natural conditions. Comparison with a plain orthogonal scheme helps to see that the Roman city is not the same template applied without changes everywhere.
Sources
For further detail and to check the information: