1) The Great Lakes, consisting of Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, form the largest group of freshwater lakes on Earth by total area. They are shared by the United States and Canada and are of significant ecological and economic importance.

2) The world's largest desert is the Sahara Desert in Africa, covering an area of about 3.6 million square miles (9.4 million square kilometers).

3) The smallest unit of time is known as a zeptosecond, which is equal to one trillionth of one billionth of a second.

4) Mount Kilimanjaro in Tanzania is the highest mountain in Africa and attracts climbers from around the world.