Cistern of the Hebdomon - Credit: Wikimedia Commons
The Cistern of the Hebdomon (), known in Turkish as Fildamı Sarnıcı ("Cistern of the elephant's stable"),Mamboury (1953), p. 326 is a Byzantine open sky water reservoir built in the quarter of the Hebdomon (today's Bakırköy), an outskirt of Constantinople.Janin (1964), p. 205 Read more on Wikipedia
Source: en.wikipedia.org