Istanbul - Basilica Cistern and Medusa Head

I love Dan Brown’s writing.  The Da Vinci Code with Tom Hanks was made into a great movie.  His book Inferno was equally good. I loved the part where the characters are underground in the Basilica Cisterns of the city about to release devastation. Well here I was down beneath the city of Instabul seeing this great cistern which served the city in time of drought and siege.  Amazing water reservoir with carp swimming happily about.  In the renovation they found two medusa head columns.  I enjoyed watching a chamber music recital done here on you tube.  What a venue.  
Just outside the entrance to the cistern where the funnel for water to enter the cistern was there was also the centre marker from which distance to other centres began.