Sahara
The Sahara Desert is about 9,000,000 square kilometers (3.5 million square miles) in size. It has been both larger and smaller at different times. After the last ice age it became more fertile, then dried up again. It is the hottest place on the Earth, but not the driest. The driest is the Atacama Desert in South America. The Sahara has about the same size as the whole United States.