That led people to the one-stage of the water cycle that offers reliable fresh water - rivers. Across the planet, rivers cover a tiny proportion of the earth's surface, but for the first farmers they became magnets. But rivers did more than supply a steady source of water, they changed the very character of the civilizations that grew up along them, influencing everything from politics to social organization. The power of rivers to shape history is graphically illustrated by perhaps the greatest of all early civilizations - Ancient Egypt. 

 

You might think you know the story, a mighty civilization that built the pyramids under the autocratic rule of ruthless pharaohs, but if you want to understand what really made Egypt great, you have to leave the pyramids and the temples behind and come here to a small place that hardly anyone visits. 

 

Here, at first glance, these look like the average, everyday 2,000-year-old steps, but this staircase is what made ancient Egypt kick. To get an idea of its true purpose, put out markings on the side wall, these grooves are carefully carved into the marble, because that’s a beautifully simple measuring device. If to see what it was measuring, you have to pop around the corner.

 

It’s all wet! Hahaha. And this is it! The Nile River. That set of steps and markings is a Nile flowmeter. It measured the changing level of the river. Each year when it flooded, the maximum height that the waters came to would directly predict the yield of the crops, and with that, the profits of the farmers made.