Roman rule collapsed in much of Mauretania and was never re-established. In 285, the emperor Diocletian reorganised what was left of the province to retain only the coastal strip between Lixus, Tingis and Septa (modern Ceuta). Although a Roman army was based in Tingis, it was decided that it would simply be too expensive to mount a reconquest of a vulnerable border region. Occupation of the city continued, however, as fine mosaics such as that of a chariot race conducted by animals in the House of Venus can not have been created earlier than the fourth century. The end of the Roman city probably came in the form of an earthquake towards the end of the century, which buried numerous bronze statues in the wreckage of the houses. After the Romans Volubilis continued to be inhabited for centuries after the end of Roman control. It was certainly reoccupied by the Eastern Roman Empire in the sixth and seventh century, when three Christian inscriptions are dated by the provincial year. By the time the Arabs had arrived in 708, the city's name was changed to Oualila or Walīlī, and it was inhabited by the Awraba, a Berber tribe that originated in Libya. Much of the city centre had been abandoned and was turned into a cemetery, while the centre of habitation had moved to the southwest of the city, where a new wall was built to contain the abridged Roman town. Volubilis remained the capital of the region well into the Islamic period. Islamic coins dating to the 8th century have been found on the site, attesting to the arrival of Islam in this part of Morocco. They are concentrated outside the city walls, which suggests that Arab settlement remained distinct from the Berber settlement inside them. It was here that Moulay Idriss established the Idrisid dynasty of Morocco in 787-8. A direct descendant of the Islamic prophet, Muhammad, he escaped to Morocco from Syria following the Battle of Fakhkh in 787. He was proclaimed "imam" in Volubilis, occupied by the Awraba, under Ishaq ibn Mohammad. He married Kanza, from the Awraba, and fathered a son, Idris II, who was proclaimed imam in Volubilis. He, too, lived outside the walls of the city, along the banks of the Wadi Khoumane, where a complex has recently been excavated that may be identified with his headquarters. Idriss I conquered most of Northern Morocco