The nature and exact location of this imperial palace cistern—whether open or covered—remain unclear. Given its proximity to the Imperial Palace, it was likely supplied by the Hadrian Waterway. Built by Justinian after the Nika riots (532 CE) to prevent future sieges, its precise location within the palace complex is unknown.
In 1913, E. Mamboury discovered a 27 × 10.5 m cistern on the slope left of the Sphendone, featuring 14 columns (6 replaced) with Corinthian capitals, likely dating to the 6th century. Another small 8-column cistern near the Justinian Palace (close to the Sea Walls) once supported the grand staircase to the palace. This cistern was emptied in 1913 by the Société des Amis de Stamboul.
