According to a legend, when Byzantine Emperor visited the Jerusalem for Helena (Empress of Constantinople), he brought along that famous Holy Grail except for the other belonging of Jesus Christ in Istanbul. After that, he built the column of Constantine (Cemberlitas) for the sake of Constantine III and kept the holy grail to protect the city in a room of that structure.
Today the people can see that fascinating structure when they visit the Grand Bazaaar. Who knows, maybe they feel the magic of the atmosphere due to holy grail.