The Italian island of Sicily is — perhaps more than any corner of Europe — a layer cake of civilizations. On one island, visitors can marvel at a well-preserved Greek temple, admire the glittering mosaics of a Norman cathedral, wander through Carthaginian ruins and feast at a market that evokes an Arabian souk.

One of my favorite places to experience Sicily’s rich stew of history and cultures is at the Norman cathedral of Monreale, just southwest of the capital, Palermo. Like the tide ebbs and flows, so does the point where Islam and Christianity meet. That comes with tension, which was sorted out as elegantly a thousand years ago as similar frictions are today.