Russia spans 11 time zones — the same moment in time is experienced as morning in Moscow and midnight in Vladivostok.

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

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

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

The Sahara Desert was once home to ancient civilizations.

The Earth's continents were once joined as Pangaea.

The Sahara Desert receives very little annual rainfall.

Iceland sits directly on the Mid-Atlantic Ridge and is actually spreading by 2.5 cm per year as two tectonic plates diverge.

The longest cave system in the world is Mammoth Cave in Kentucky.