5,000 years ago, it wasn't just the ancient Egyptians who noticed the value of rivers. Other great civilizations were also forming along the banks of rivers. 

 

In Mesopotamia, the Sumerian civilization flourished between the Tigris and the Euphrates. Further east, the Harappan civilization formed by the Indus. And early Chinese civilizations were emerging along the Yellow River.

 

But not all early farmers were content to settle by rivers. Others learned to exploit new sources of water in the unlikeliest places like the Sahara Desert in Libya.

 

These are the remains of the ancient city of Garama, which about two and a half thousand years ago was the center of a powerful empire.

 

Today, it's a bit of a maze, but from up here, you can see the shapes of the buildings, the way the streets interconnect. But the real sense of how this place is to walk to its prime. That was the home of the Garamantians, which for me are rather forgotten people. They have been eclipsed in the history books by the showy contemporaries, the Greeks and the Romans. The Garamantians dominated the Sahara Desert for almost 2 thousand years.