Emi Koussi also known as Mount Koussi is a high, extinct shield volcano in the Tibesti massif of Chad. Emi Koussi is the highest peak in the Sahara and the highest peak in Chad. At the summit is a vast crater with a rare system of two calderas one inside the other. 1)
The Sahara is mostly stony hamada covered with rocky debris. Ergs (sandy areas covered by dunes) make up only about 20% of the total area. 2)
Lakes of Ounianga are a group of 15 lakes in northern Chad. The lakes have an elongated shape and are stretched in the north-south direction, which is caused by the activity of the trade winds. The lakes form a hydrological system not found in any other desert in the world. The trade winds carry sand into the basin, creating fifteen lakes separated by dunes. The lakes are fed by groundwater. 3)
Ahaggar (English: Hoggar) is a mountain range in the central Sahara in Algeria. The Ahaggar consists of numerous mountain groups with leveled tops, above which rise the cones of extinct volcanoes. The massif is cut by a dense network of dry valleys (wadis). Numerous prehistoric rock paintings have been discovered in the area of the massif. 4)
The Sahara Desert is the largest non-polar desert in the world (ahead of Antarctica and the Arctic if the criterion is extremely low rainfall). It is located in 11 countries: Morocco, Algeria, Tunisia, Libya, Egypt, Western Sahara, Mauritania, Mali, Niger, Chad, and Sudan. What is very interesting is that despite the very high temperatures in its areas, even snowfalls have occurred there (e.g. in 1976, 2016, or January 2018). One of the world's oldest stone solar calendars has been found in the Sahara, which dates back to between 5500 and 4500 BC. 5)