Sultanahmet Camii (Blue Mosque), Istanbul

Dubbed the “Blue Mosque” by Europeans because of its beautiful interior ceiling tiles (famed Iznik tiles), Sultanahmet Camii is the only mosque in the world with six minarets. Built by Ahmet I between 1609 and 1616, the architect was Sedefhar Mehmet Ağa, one of Mimar Sinan's most prominent students. Inside, it's surprisingly small, though very detailed, and the city has installed a lovely wrought iron chandelier at the entrance. The shrine near the mosque houses the tombs of Ahmet I and his wife Kosem Sultan. The Blue Mosque is a working mosque, so non-worshiping tourists are not permitted to enter during prayer times, which occur 5 times daily for 30 minutes each.