The video below will give you the Mainstream History of this amazing place.
Two undeniable facts are told in it. There is a huge cistern close by the Hagia Sophia and there is an aqueduct bringing fresh water from the forests of Belgrade.
My belief is that this cistern served the Topkapi Palace of Suleiman the Magnificent and that it was built around the same time as the palace – in the 1400’s.
But the MS history is much more entertaining, yes :o)