Blue Mosque (Sultan Ahmed Mosque)

Sultan Ahmed was determined to build a mosque that rivaled the nearby Hagia Sophia and most would agree that he accomplished this task -- or at least came close. Since the early 1600s the Blue Mosque has been quite the sight to behold, with a flurry of domes, semidomes and minarets. It's also one of the biggest tourist draws in Istanbul.

Remember that it is an active religious site, so dress conservatively. Women should wear headscarves, as is the custom. If you forget to bring one, you can borrow one from the mosque.

The Blue Mosque is located in the Sultanahmet neighborhood. It is open daily from 9 a.m. until 5 p.m. There is no entrance fee, but admission is restricted during prayer service, especially on Fridays.