Column of Leo
The Column of Leo was erected by his sister Euphemia, for her brother Leo I (457-74) on the acropolis at the Pittakia northeast of Hagia Sophia, now in the area of Topkapı Palace.
In the late 1950s and early 1960s, several fragments of a marble column were uncovered in the second court of the Topkapı Palace. Later it was argued that the pieces belong together, leading to the identification with the Column of Leo. It seems to have been around 26 meters tall, making it one of the tallest columns in the city. Among the fragments were a Corinthian capital with a small human faces, an impost block with a frieze of large acanthus leaves (which sat upon the Corinthian capital, a complete column drum decorated with a laurel wreath and a single christogram (Chi-Rho), and a similar fragment of another column drum.
While the Colossus of Barletta has been associated with the Column of Marcian, its scale seems to be too large for the column. However, the statue is more compatible with the remains found in the garden of Topkapı Palace. It has been suggested that a column drawn by Melchior Lorichs in 1561 represents this column, though it is more commonly attributed to the Column of Constantine.
Sources
The Cambridge Ancient History: Late Antiquity, Empire and Successors edited by Averil Cameron
Column of Leo (Oxford Late Statues of Antiquity)
Resources
Column of Leo (Byzantine 1200)
Columns and Monuments of Constantinople Photo Album (Byzantine Legacy Flickr)