The Early Centuries - Byzantium 01, Page 50

  Later it was roofed over and used as a cistern, on which the palace of Romanus was built.

  *** WALLS

  The oldest part of the walls which surround the city to the west of the Golden Horn dates from the time of Constantine; but by far the greatest length - including almost all the present Land Walls - is essentially the work of Anthemius, Prefect of the East under Theodosius II, who completed them in 413. The Land Walls and those along the Marmara are continuous; those lining the Horn have largely disappeared.