The Itaipu Dam blocks the Paraná River exactly where Brazil meets Paraguay.
The wall is not one nation's alone.
A joint company owns it in equal halves: Brazil through Eletrobras and Paraguay through ANDE.
Twenty generating units deliver 14,000 megawatts.
In 2016 the plant produced 103.1 terawatt-hours.
One year. One world record for annual output from a single plant.
The American Society of Civil Engineers lists it among the Seven Wonders of the Modern World.
The surprise is not the concrete.
Half the units run at 50 hertz, the rate Paraguay's grid needs.
The other half runs at 60 hertz, because Brazil uses another frequency.
Water drops once, and power leaves in two standards.
One dam.
Two grids.
How much of Paraguay runs on this?
About 86.3 percent of the country's use.
The small neighbor leans on the wall. The big one shares the same water at a different frequency.
Itaipu is more than a concrete border.
It is a plant that speaks two grids at once.
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