By Mohamed El-Hebeishy FIFTY million years ago it was mostly submerged by what is known as the Tethys Sea, while during the Roman era it was described the breadbasket of the Roman Empire. Join Mohamed El-Hebeishy as he sets out to unveil Fayoum, Egypt's largest oasis Qasr Al-Sagha, or rather the Golden Fortress, is one of Fayoum's mysterious marvels. Located north of Lake Qarun, the building once stood on the shore of the ancient Lake Moeris. Now the lake has shrunk and Qasr Al-Sagha is stranded amidst the barren desert. So what makes this archaeological site peculiar? Several other reasons besides the location. Though it has been debatable for some time, scholars have agreed that it belongs to the Middle Kingdom. However, the purpose of the edifice is not known, or whether it is a temple or a palace. Containing a number of small rooms, perhaps shrines, as well as a blind room with no entrance, the whole of the building is left bare without a single inscription or decoration. Qasr Al-Sagha is a job never completed. To add to the puzzle, the construction technique Qasr Al-Sagha's architecture followed was also unique and unusual. The edifice is built of large limestone chunks fitted together like a jigsaw puzzle with supporting corner joints. There is absolutely no mortar used in its build. Qasr Al-Sagha was discovered by German explorer Georg August Schweinfurth in 1884. A resident in Egypt who lived in Helwan for over 35 years, Schweinfurth was also an archaeologist, geologist and botanist who under the patronage of Khedive Ismail founded the Royal Geographic Society of Egypt. In addition to his discovery of Qasr Al-Sagha, Schweinfurth pioneered fossil exploration in the vicinity of Fayoum, and was credited for his remarkable discovery of Zeuglodon, the ancient whale. Qasr Al-Sagha is reachable in a 4W on a 25-kilometre dirt road that branches out from Kom Ushim. Though the terrain is fairly manageable, it is advisable to be accompanied by a guide.