This is one of the four surviving Byzantine honorific columns in Istanbul, it was hidden in a private garden until a fire in 1908 led to a replanning of the district, the column became the centre of a small square. It is made of red-grey Egyptian Syenitic granite on a high marble pedestal, the column is surmounted by a Corinthian capital and a plinth with eagles at the corners. A statue of the Emperor must have been on top. On the base a Victory in high relief is visible, as well as a text indicating the column was erected by prefect Tatianus in honor of the Emperor Marcian (450-457). A notice gives it as:
Principis hanc statuam Marciani cerne tovuque. Praefectus vovit quod Tatianus opus.
Observe this statue of the princeps Marcian and its base. A work dedicated by the prefect Tatianus.
The Turkish name is Kız Taşı (maiden’s Stone), probably because of the Victory. Because in the same neighbourhood a Column of Venus stood, with the power to distinguish true virgins from false ones, the Marcian column has been confused with the other one.

I came across a site with reconstructions of Istanbul monuments around 1200, for instance the Column of Marcian.