THE city of Istanbul, site of many a civilizations over the centuries, is no doubt renowned for the interesting combination of eastern and western elements it presents; mosques and churches, bazaars and columns are scattered all over the old city. But beneath this very well known and well documented surface is another layer, as old and as valuable as the upper one, though much less known: the water system of the city, built by the Romans and the Byzantines. CONSISTING of open and covered cisterns, interconnecting underground canals and aqueducts, this complicated and vast water distribution system is both a technical achievement and an artistic marvel. In a large area extending from the Theodosian Walls to the Saray Point (Saray Burnu) are numerous cisterns of various sizes and shapes, looking more like underground palaces, with their columns and vaults, than water reservoirs. BEFORE relating a short historical background of the cisterns and indicating their types and locations, it is essential to consider the importance of such a water system in the city of Constantinople. Although surrounded by water on three sides, the city was built on a particularly dry land and therefore there was the need to bring water from sources outside the city. The aim was both to bring water to the city and to store it. The city was subject not only to periods of drought, but also to frequent and long lasting sieges, during which water canals outside city walls could be destroyed by the enemy, and it was of vital importance to keep the people and the army well supplied and provided for. Hence open and covered cisterns were built all over the city, and during the Byzantine Empire all the palaces and the majority of churches, monasteries and rich houses had their own underground cisterns. The construction of these substructures was begun at the time of the Emperor Constantine, in mid 4th century, and continued in the following centuries; in particular after the disastrous Nika Revalt of 532, during which much of the city was destroyed, the Emperor Justinian undertook an extensive restoration and enlargement of these cisterns.......

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