Introduction to Fossil Valley: On the Gobi Desert on the west side of the Nile River, 25 kilometers north of Khartoum, there is a small ditch washed by a seasonal river. A lot of petrified wood fossils are exposed near the ditch. Some are upright, some are lying horizontally, and some have very complete trunks and branches. The longest ones are more than 20 meters long and more than 1 meter thick in diameter. The appearance of a large amount of petrified wood shows that this endless Gobi Desert was once a forest with towering trees in ancient times.