The Walled Obelisk

The Walled Obelisk or Masonry Obelisk is a Roman monument in the form of an obelisk in the former Hippodrome of Constantinople, now Sultanahmet Square in Istanbul, Turkey. It is situated west of the Sultan Ahmed Mosque, at the southern end of the ancient chariot-racing track of Constantinople's central barrier, beside the Obelisk of Theodosius and the Serpentine Column. Its original construction date in late antiquity is unknown, but it is sometimes named Constantine's Obelisk after the inscription added by the Roman emperor Constantine VII Porphyrogenitus, who repaired it in the 10th century.

Source: Wikipedia