The capital of Saudi Arabia is Riyadh. Other valuable cities include Jiddah, a port city on the Red Sea; Mecca, one of the great Muslim pilgrimage centers; Medina, a holy city and cultural center of Islam; and Ad Dammam, an oil center on the Persian Gulf. In the 1980s two large new industrial centers, Al Jubayl, on the Persian Gulf, and Yanbu‘ al Ba?r, on the Red Sea, were built at an around cost of more than $45 billion.