Americas' earliest observatory unearthed

Archaeologists working high in the Peruvian Andes have discovered the oldest celestial observatory in the Americas -- a 4,200-year-old structure marking the summer and winter solstices that is as old as the stone pillars of Stonehenge.

The observatory was built on the top of a 33-foot-high pyramid with precise alignments and sight lines that provide an astronomical calendar for agriculture, archaeologist Robert Benfer of the University of Missouri said.