Hagia Sophia in Istanbul Turkey
The name means Holy Wisdom. Built in only 6 years, 532 to 537, it was the largest Christian Cathedral in Constantinople. Previously two other churches by the same name were built on the same space but had been destroyed in riots. In 1054 it became a Greek Orthodox Cathedral and a Roman Catholic Cathedral in 1204. In 1261 it went back to a Greek Orthodox Cathedral until 1453 when the Ottoman Empire changed it into a Mosque.
In 1931 it was closed for four years and reopened in 1935 as a museum. In 2014 it was ranked as the second most visited museum in Turkey with an average attendance of almost 3.3 million per year. In 2015 it was the most visited tourist attraction in Turkey.
Initially, there was only one minaret. Now, there is one pink one and three white ones which are the newest.
In spite of the amazing architecture of the time, the highlight is the three domes with windows to let in light and to reduce the weight of the domes.