The Sahara desert was a green savanna as recently as 5,000 years ago.

The Sahara Desert is roughly the same size as the United States.

The United States has no official language — English is the dominant language but is not legally designated.

The Pacific Ring of Fire contains many of the world's active volcanoes.

More people live in Asia than the rest of the world combined.

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

Zhangye once stood along the Silk Road as a trade hub.

The Trans-Siberian Railway is one of the longest railway lines in the world.

The shortest commercial flight in the world operates between two Scottish islands — Westray to Papa Westray — lasting about 90 seconds.