The Siwa Oasis is an urban oasis in Egypt. It is situated between the Qattara Depression and the Great Sand Sea in the Western Desert, 50 km east of the Egypt–Libya border, and 560 km from the Egyptian capital city of Cairo. The geology is characterised by horizontal layers of porous limestones alternated with marls and clays dating back to the Miocene. Two large salt lakes are fed by drainage water of agricultural origin. The oasis supports the cultivation of thousands of date palms and olives.