In 1984, I visited Colorado State University, my alma mater, to attend a retirement dinner for one of my professors. The following day, I traveled to Denver to visit an acquaintance from my college days at CSU in the early 1970's.

In the evening, we went to a slide presentation in the local community center. A lady was showing the pictures she had taken in a recent trip to Peru. Among the photos were several slides of the terraces of Pisac, without a doubt some of the most impressive and best preserved agricultural terraces built by the Incas.

At the end of the presentation, in response to questions from the audience, she proclaimed: "Nobody knows how the Incas pumped the water from the streams to the terraces."

Obviously, she had missed the fact that the terraces held the runoff, eliminating the need for pumping.


The agricultural terraces at Pisac, Peru.

The agricultural terraces at Pisac, Peru.