The Roman ruins at Volubilis. Volubilis grew rapidly under Roman rule from the 1st century onward and expanded to cover about 100 acres with a 1.6 mile circuit of walls. The city gained a number of major public buildings in the 2nd century, including a basilica, temple and triumphal arch. Its prosperity, which was derived principally from growing olives, prompted the construction of many fine townhouses with large mosaic floors.