Istanbul has a very rich history!!! I went straight from the airport to a hotel meeting to a city tour... Crazy Day! Crazy Tired!
The Basilica Cistern below was built in 532. There are 336 marble pillars that support this underground water supply for the city. During restoration two of the pillars were discovered to be the heads of Medusa.
Saint Irene Church is on the grounds of the Topkapi Palace (the Sultan's Palace of the Ottoman Empire - 1478) and was first built in the 4th century. Today it is used for many musical and cultural performances.
And Saint Sophia, also in the old town, is Istanbul's largest and oldest structure - 1500 years.
Sophia served as a Christian Church for thousands of years, then converted to an Islam Mosque for 500 years and the Istanbul Government made it a place of humanity and a museum 75 years ago. When the church became a Mosque the christian murals were covered with plaster and Islam discs were hung. As the restoration of Sophia continues it has been discovered that the plaster preserved much of the Christian art.