Ayasofya (Hagia Sophia / St. Sophia), Istanbul

The magnificent Ayasofya was originally built by Byzantine Emperor Justinian in 537 AD, and it was used as a church for 916 years. It then became a mosque for 481 years, and Turkey's first President, Atatürk, declared it a museum in 1935. (It is no longer used as a place of worship, so you needn't be too concerned with your dress or the appropriateness of taking photos as you should be at some other religious landmarks in Istanbul, such as the Blue Mosque .) Considered the first and last unique application in terms of its architecture (it was built on a square base rather than the common rectangular one), magnificence and functionality, it has been the inspiration for Ottoman mosques for countless centuries. The incredible frescoes and mosaics in the upper gallery, despite being damaged, are among the most visited sites in the city. From 2007-2008, each and every gold tile piece of the ceiling wil l be restored to its former glory. Ayasofya is a number one must-see in Istanbul.