Cistern of the Hebdomon

The Cistern of the Hebdomon (Greek: κινστέρνη τοῦ Ἕβδομου), known in Turkish as Fildamı Sarnıcı ("Cistern of the elephant's stable"), is a Byzantine open sky water reservoir built in the quarter of the Hebdomon (today's Bakırköy), an outskirt of Constantinople.