The city of Istanbul has important water system remnants from old civilizations among which water line systems begun with Byzantine period and continued during Ottoman era, including Kırkçeşme water supply system. The original gallery structure within the Kırkçeşme system has been altered with time at some places as a result of necessary planning activities, restoration and repair works. All these activities helped to keep almost the system originality. Since its first opening in 1564, its discharge increased steadily as a result of additional drainage feeding line connections to the main gallery. However, through time only a couple of the 570 additional lines have remained in operation. Although other similar establishments have perished in time without leaving even traces, the Kırkçeşme system is its vivid and harmonious appearance in front of eyes even today. Four dams were constructed at the most convenient locations along the water supply lines from 1620 to 1818. The water from the streams was collected during the rainy season and discharged to the city at times of need with increasing capacity. In general, the Kırkçeşme system has two branches: one extends towards the east, which seemed to have more water, due to its feedback from the Kirazlı, Topuz and Paşa tributaries of the Kağıthane stream; the other branch is westwards which is fed by the Ayvad Deresi, Orta Dere and Bakraç Dere tributaries of the Kağıthane stream. All the water are brought together at Başhavuz (main pool) south of Kemerburgaz, where they collectively enter the main supply line crossing the Alibey Stream over the Mağlova Aqueduct, and then joining a branch from the Cebeciköy Stream and finally flow in towards the south. In a historical document called Tezkiret'ül Bünyan, (The Book of Structures) the author states that Sinan pledged to the Sultan about the existence of some old waterways. However, the Roman waterway still remains in the vicinity of Cebeciköy, which is located at a higher elevation than the Kırkçeşme water supply line but ran parallel to it. The water supply system should have integrated perspective for operation and maintenances. On the other hand, standing structures give to humanity the impression that the stability and design carry not only water, but also valuable cultural heritage. Moreover, they connect many civilizations with each other and also past as well as future.