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In the coastal desert of Peru lies a strange structure some 2300-years-old, consisting of what appears to be a fort atop a hill, but with a vertebrae-like line of 13 towers constructed on a raised area to its south-east.

The fort is odd from a military point of view because it would have been almost impossible to defend: it has numerous entrances and no source of water inside. Then there are the towers, which are several hundred metres from the hilltop fort, lie in a straight line and serve no discernible defensive role.

So in 2007, archaeologists put forward a new interpretation. They suggested the site may have been a place of worship and a solar observatory, like Stonehenge, rather than a fort.

Their main evidence was that the towers line up with the sunrise on important dates such as summer and winter solstice.

Today, Amelia Sparavigna at the Politecnico di Torino in Italy adds some evidence using a program developed for calculating the position of the sun in the sky to determine how much sunlight should fall on solar panels.

According to Sparavigna, “the observing points are situated so that, on the solstices, the sunrises and sunsets line up with the towers at either end of the line, suggesting that this ancient civilization had a solar calendar”. She goes on to suggest that this method of observing the sun’s path during the year may have been used to help determine the optimum time for planting crops.

Ironically, Sparavigna also notes that the ancient archaeological site is now sadly under threat from new construction work planned by…agricultural companies.

Download the paper from Arxiv.org