Being one of the biggest domed cisterns in Istanbul, the Basilica Cistern fascinates people who see or visit it. Harvesting rainwater, which was practiced by nearly all of the past civilizations, is the easiest and most environment-friendly way of collecting water. Although this practice was a standard in many historical houses around the Eyüp district of Istanbul, it has now evolved into a forgotten practice. However, this could be one of the cheapest and most practical solutions for our region, which is heading towards being a water poor area. Being one of the practices that are enormously valued by the Government of Australia, rainwater harvesting is now actively practiced by more than 5 million Australians. As an example from our region, the amount of precipitation per square meter is 574 mm in Turkey; therefore we can say that if water harvesting is practiced in the entire roofspace of Turkey, which amounts to one billion square meters, 574.000 tons of water can be harvested, in addition to the present water reservoirs. In other words, the daily water requirements of more than 2,5 million people can be addressed by this way! One thing is certain: it will be very useful if we can adapt these environment-friendly practices into today’s world!