At the old Istanbul, every two hundred meters there is one water fountain. Water is very important in Islam, not only to drink but also to perform ablution five times a day. In Islam, there is an idea of recording angels on your right and left shoulders. What good and bad act you made they write. When you passed away they stop writing, except if you left something for other human beings.
Water was one of the most important things that people may pray and remember you when they drink from your fountain.
This is one of the reasons why there are a lot of fountains in Istanbul.