Ibiza became important enough for its capital to be allowed into a federation with Rome, enjoying a certain degree of autonomy that gradually eroded away. By the time Ebusus was fully incorporated as a Roman colony in the year 74 AD, the last traces of Carthaginian structures had all but disappeared. The 3rd century AD was a low point for an empire in decline but again, its commanding position astride the trade routes of the western Mediterranean kept Ibiza going as a strategic commercial center. Then came the Vandals in 455 AD and 80 years later, the armies of Byzantium, to conquer the Balearics. For this period, details of what specifically was going on in Ibiza are scarce.
Ibiza's first contacts with the Islamic world go back to the beginning of the 8th century. By 902, the Illes Balears had become the easternmost domains of Al-Andalus, until the caliph of Denia seized them in 1014. After several unsuccessful attempts to wrest control of Medina Yebisah away from the followers of the prophet, Ibiza and Formentera were finally conquered by Catalan Christians in the year 1235. Illustrating vividly Ibiza's historical and anthropological evolution from the prehistoric to the Islamic eras are the exhibits and artifacts in the Dalt Vila Archaeological Museum. The visitors' guide, prepared by Benjamí Costa and Jordi Fernandez, gives a most thorough account of the objects on display.
On 8th August 1235, Ibiza fell to combined Catalan-Aragonese forces under the command of Guillem de Montgrí. That day is still celebrated as a local holiday since it marked the beginning of an extended period of self-government that did not end until 1715, when it was abruptly curtailed by a decree issued by Spanish King Phillip V, abolishing the Universitat, the local lawmaking body.
Not until the Spanish Constitution of 1978,
did Ibiza regain control over its own affairs. The Self-Government
Statutes of 1983 granted extensive powers to the Autonomous Community
of the Illes Balears as well as setting up self-governing bodies,
or Consells: one for Menorca, one for Mallorca and another for
Ibiza and Formentera.