Aqueduct of Valens

This is a Late Roman and Early Byzantine period aqueduct built probably around 4th century AD connecting two hills (out of seven) of ancient Constantinople over this little valley. It's known as the Aqueduct of Valens, and today local people call it as Bozdogan Kemeri (Arch) in Turkish. Originally it was used to bring water to Istanbul from the springs of Belgrade forest,in Sariyer, about 30 km north of Istanbul.Once in the city, the water was stored in several underground cisterns, like the Basilica Cistern.Once there was a monumental fountain in Beyazit square and this aqueduct was bringing water to this fountain also.During the late Byzantine period it wasn't used much and fell into ruins, than restored by the Ottomans after the Conquest of Istanbul and served for some time to carry water again. Over the centuries, it was badly damaged because of disuse and roads and buildings constructed on and around it. Today only bits and pieces left from the original aqueducts on its way from the forest to the city center, and in Sarachane neighborhood there is a 900 meter long part of it, namely Bozdogan arch. The Municipality of Istanbul started the restorations in 1998.

It is situated on the European side of Istanbul,in Unkapani,which belongs to Fatih district.

Source: http://www.allaboutturkey.com