At least 2,300 years ago, Paracas people in the Chincha Valley of Peru were engineering their landscape to keep time and host ritual and social activities. Two U-shaped structures, and possibly more, were built to mark the sunset of the winter solstice. Other structures formed discrete clusters for sacred and secular events, and lines of rock pointed the way to the celebrations, scientists argue May 5 in the Proceedings of the National Academy of Sciences. The engineered landscapes are several centuries older than the Nasca geoglyphs and suggest that the earlier forms brought together highland and coastal Paracas groups, the scientists say.