Ethiopia is the tenth largest country in Africa, covering 439,580 square miles (1,138,512 square kilometers) and is the major constituent of the landmass known as the Horn of Africa. It is bordered on the north and northeast by Eritrea, on the east by Djibouti and Somalia, on the south by Kenya, and on the west and southwest by Sudan.
The central plateau, known as the highlands, is surrounded on three sides by desert with a significantly lower elevation. The plateau is between six thousand and ten thousand feet above sea level, with the highest peak being Ras Deshan, the fourth-tallest mountain in Africa. Addis Ababa is the third-highest capital city in the world.
The Great Rift Valley (known for discoveries of early hominids such as Lucy, whose bones reside in the Ethiopian National Museum) bisects the central plateau. The valley extends southwest through the country and includes the Danakil Depression, a desert containing the lowest dry point on the earth. In the highlands is Lake Tana, the source of the Blue Nile, which supplies the great majority of water to the Nile River Valley in Egypt.
Variation in altitude results in dramatic climatic variation. Some peaks in the Simyen Mountains receive periodic snowfall, while the average temperature of the Danakil is 120 degrees Fahrenheit in the day time. The high central plateau is mild, with a mean average temperature of 62 degrees Fahrenheit.