The Blue Nile is one of two main rivers that come together far to the north to make the Nile, the famous river of Egypt and Sudan. The Blue Nile starts in Ethiopia, in a lake called Lake Tana. A short way after the lake, the river suddenly tumbles over the edge of a giant cliff and crashes down 45 metres into a deep gorge.
When the water hits the bottom, so much mist sprays into the air that you can see the cloud from a long way off - and it really does look like smoke. Rainbows often form in the spray when the sun is out. On a wet-season day the falls can be more than 400 metres wide - wider than four football pitches end to end.
Most of Egypt's famous Nile water - the river that grows the crops and supplies the cities of Egypt - comes from the Blue Nile, not from the other branch. So the rain that falls in Ethiopia ends up watering farms thousands of kilometres away.
The falls are also a home for fish, birds, baboons and bright green mosses growing in the constant spray. Visitors can walk across a 17th-century stone bridge nearby to get a view of the whole thunderous curtain of water.