In fact, the superstructure is estimated to hold an almost inconceivable 200 quadrillion (that's 200 followed by 15 zeros) ...

A quipu is an ancient recording device used by Andean civilizations, and particularly the Incas. It consists of a series of colored strings of various lengths, with knots tied in different positions.

From the quipu to the conquistadors ... in our series on the Inca Empire. #ExtraHistory #IncaEmpire #History Nasa astronaut trapped in space ventures outside for first time in months Walmart ...