There are few dams in the world that capture the imagination as much as Belo Monte, built on the “Big Bend” of the Xingu river in the Brazilian Amazon. Its construction has involved an army of 25,000 workers working round the clock since 2011 to excavate over 240m cubic metres of soil and rock, pour three million cubic metres of concrete, and divert 80% of the river’s flow through 24 turbines.