The Nasca lines are geoglyphs – arrays of stones forming geometric shapes constructed by ancient humans, the largest ones occupying areas of more than 1km2. The authors used optically stimulated luminescence dating of quartz buried when the stone lines were constructed to give new dates for contexts associated with geoglyphs on high mesetas near Palpa. They conclude that the stone lines at sites at San Ignacio and Sacramento were constructed between AD 400 and 650. This suggests that they were made in the later part of the Early Intermediate Period by people of the Nasca culture.