Ain Dalla, some 75 kilometers (46 miles) northwest of Farafra Oasis, is an uninhabited depression with a freshwater source. As the last spring before the Great Sand Sea, Ain Dalla has always been of strategic importance.
Gilf Kebir National Park
The Gilf Kebir, also known as the Gilf al-Kebir, is a massive 300 meters (980 feet) high, gigantic plateau equivalent to the size of Switzerland. While today the Gilf Kebir is one of the most inhospitable places on Earth, a few thousand years back it thrived with life, green fields, zigzagging rivers, and a bounty of game. Early hunter-gatherers who lived here left us their mesmerizing rock art depicting their daily lives. The best-preserved paintings are found in the Cave of Swimmers and the Cave of Beasts (also known as Mestikawi-Foggini Cave or Foggini Cave).
Great Sand Sea
Between the Gilf Kebir and Siwa Oasis lies the awe-inspiring immensity of dune fields that the German explorer Gerhard Rohlfs aptly named the Great Sand Sea (Bahr al-Raml). Covering a colossal 72 000 square kilometers (27 800 square miles)—approximately the size of Ireland—the Great Sand Sea extends for an average of 650 kilometers (404 miles) from north to south and 300 kilometers (187 miles) from east to west. The Great Sand Sea is home to some of the largest dunes in the world, measuring sometimes more than 100 meters (328 feet) in height and as much as 150 kilometers (93 miles) in length.
Silica Glass Field
On the southern shore of the Great Sand Sea, close to the Libyan border, we find one of the greatest mysteries of Egypt: the Silica Glass Field. The origin of this glass is a controversial issue for the scientific community: Some scientists argue that lightning strikes might be the cause, while others make the case that desert glass is the result of a meteor impact; still others insist that desert glass is of volcanic origin.
The Silica Glass Field covers an area that measures roughly 130 kilometers (80 miles) north and south by 50 kilometers (30 miles) east and west. The desert glass found in the Silica Glass Field is of extraordinary purity—approximately 98 % pure silica—and comes in various shapes (buttons, teardrops, dumb-bells, rods, spheres, or disks). Although commonly about 2–3 centimeters (1 inch) in diameter, they range up to a maximum diameter of almost 30 centimeters (12 inches) and weigh as much as 12 kilograms (28 pounds).