COA, the river of a thousand engravings

Along the banks of the peaceful Coa river in Portugal lies an archaeological treasure: thousands of open-air prehistoric engravings. Their discovery in the 1990’s created quite a stir, comparable only to the discovery of cave art which until that time was considered the most important kind of prehistoric art in the area.
The film was made when an extraordinary event took place: the artificial lowering of the river’s water level.
This resulted in a revolution in the study of prehistory.