The Great Wall of China has been attempted as a marathon route — participants run over 3,700 steps.

The Earth's crust varies in thickness beneath continents and oceans.

The Caspian Sea is technically the world's largest lake, covering 371,000 square kilometers.

The Sahara Desert is one of the largest deserts in the world.

Angel Falls in Venezuela is the world's highest uninterrupted waterfall at 979 meters.

The Gobi Desert is the fastest-expanding desert in the world and covers parts of northern China and southern Mongolia.

Australia is wider than the Moon — Australia is about 4,000 km across, the Moon's diameter is 3,474 km.

There are places in Antarctica where no rain has fallen for millions of years.

The tallest waterfall in the world is Angel Falls in Venezuela.