The Great Green Wall initiative aims to restore 100 million hectares across the African Sahel by 2030.

Vatican City is the world's smallest country — it covers just 0.44 square kilometers.

The Caspian Sea is the world's largest inland body of water and is classified as a lake despite its salt water.

The Colosseum in Rome was completed in the first century.

The Great Rift Valley in Africa may eventually split the continent in two, forming a new ocean in millions of years.

The Pleistocene epoch included repeated glacial cycles.

The Earth is about 4.5 billion years old.

Australia is wider than the Moon.

The Earth's crust is thinner beneath oceans.