Historically the 4,000-kilometer Mediterranean boundary has fluttered. Population centers north of it in Europe have invited contact and Arab exploration—mostly friendly, though sometimes not. Islands and peninsulas near the Arab coast have changed hands. The islands of Sicily and Malta lie just a hundred kilometers east of the Tunisian city of Carthage, which has been a point of contact with Europe since its founding in the first millennium BCE; both Sicily and Malta at times have been part of the Arab World. Just across the Strait of Gibraltar from Morocco, regions of the Iberian peninsula were part of the Arab World throughout the Middle Ages, extending the northern boundary at times to the foothills of the Pyrenees and leaving a substantial mark on local and wider European and Western culture.