To my amazement this cistern (storage for drinking water) was within a hundred meters from an hotel where I stayed four times before, without ever even knowing it existed. One day I found an opened door, and a flight of stairs ... The cistern is much larger than I can show, since part of it is walled in. It is more than a third the size of the Yerebatan Saray, a famous cistern. It was probably started by Philoxenus, a Roman senator who came to the city with Constantine the Great. A notice outside indicates it was built by (maybe enlarged?) in 428-433 under Theodosius II, second emperor of the Byzantine empire after Arcadius. Binbirdirek means "with a 1001 pillars".