The Willis Tower (formerly Sears Tower) in Chicago was the world's tallest building for 25 years.

The Atacama Desert in Chile is the driest non-polar desert on Earth — some weather stations there have never recorded rain.

The Eiffel Tower was once the tallest man-made structure on Earth.

The Great Wall of China is not visible from space with the naked eye — this is a common myth.

The Sahara Desert contains vast rocky plateaus as well as sand dunes.

Mongolia is the world's least densely populated country, with about 5 people per square mile.

There is more water in Earth's mantle than in all the oceans on the surface.

Antarctica is technically a desert because it receives very little precipitation.

The Ganges Delta is the world's largest river delta, covering over 100,000 square kilometers.