The Geoglyphs of Acre
When the Amazon forest was cleared in western Brazil, huge geometric ditches appeared in the ground: perfect circles and squares, hundreds of metres across.
What was reported
As forest was cleared for cattle ranches in the Brazilian state of Acre, people began to notice huge earthworks: deep ditches dug in perfect circles, squares and other shapes, some more than 300 metres across, often linked by straight roads. A palaeontologist, Alceu Ranzi, saw many from a plane in the late 1990s and drew attention to them.
More than 450 are now known. For many people they came as a shock: the Amazon was supposed to be an untouched wilderness.
Explanations offered
Archaeologists date the earthworks to roughly 2,000 years ago. They appear to have been ceremonial sites rather than villages or forts. Studies of ancient pollen suggest the builders managed the forest around them rather than clearing it wholesale.
- When
- Built about 2,000 years ago
- Where
- Acre, Brazil
- Witnesses
- Pilots, archaeologists and ranchers
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.