On reaching the site of Cumbe Mayo, the visitor is struck by the eroded rocks that seem to have eerie human shapes (los Frailones). Petroglyphs have been found inside a cavity. The Cajamarca Indians dug an amazing aqueduct, nearly 9km-long, here right out of the rock. Dating back to around 1500BC, it carried water from as far away as the valley, and represents yet another demonstration of the pre-Incan civilisations' engineering ingenuity.