In the center background are two columns:
The nearest is an Egyptian Obelisk from the 15th century B.C. brought to Constantinople 390 C.E. from Cairo. The coarse column is of unknown origin. It was originally bronze plated. Members of the 4th Crusade removed the bronze to use in armor manufacture.

The Hippodrome is where the ancients had their chariot races. The columns were the end posts to mark the place to make the return circuit.

The Blue Mosque is just to the left of the site of this picture.