As access to water was the top priority for the inhabitants of arid and semi-arid regions in the ancient world, the Qanat System was one of the most popular methods adopted to make the best use possible of the subterranean water streaming down  the foothills, for both irrigation and daily use. This paper, first, will provide a historical overview of the Qanat Systems in ancient world: their geographical distribution and possible origin. Then, the study will focus on the Qanat System of Qasr Allam in Bahariya Oasis, Egypt, as the case study. Qasr Allam is considered as one of the richest Qanat Systems in Baharyia Oasis and a perfect example in Egypt to give more insight on its historical and geological significance. We will trace the remains of the Qasr Allam Qanat lines still existing, using the modern scientific methods including maps by Google Earth and the analysis of the satellite images. Therefore, the current study is considered a documentation work.