Large-scale deforestation in South-West Amazonia has recently uncovered previously hidden geometric earthworks. The existence of these so-called ‘geoglyphs’ challenges the traditional view of pre-Columbian cultural development in the hinterlands of Amazonia. Archaeological work, including remote sensing and ground survey, has so far identified 281 geoglyphs in an area of about 20,000 sq. km. The Fazenda Colorada geoglyph has received a lot of archaeological attention because of its remarkable complexity: it exhibits a long construction history, from about the first century AD to around AD 1400, and has an on-going archaeological programme of excavations by the Brazilian-Finnish project partners. The environmental impact of the geoglyphs builders is, however, still mainly unknown.