Archaeologists have used high-resolution satellite snapshots to finally piece together a mystery surrounding the ancient people of Peru's famous Nasca region.
The mystery centres around a series of carefully built, spiralling holes called puquios, burrowed into the ground in the Nasca Desert of southern Peru. These peculiar formations could not be dated using traditional carbon dating techniques, and the Nasca people didn't leave behind any evidence of when they were first established, so archaeologists have spent centuries trying to figure out their purpose in vain.
Now, Rosa Lasaponarac from the Institute of Methodologies for Environmental Analysis in Italy describes how she studied imagery shot from space to plot the distribution of the puquios and how they were related to nearby settlements - settlements that happened to be easier to date.
As BBC Future reports, this provides insight into how this network of tunnels and caves was created in Nasca. It's now believed that the primary aim of the puquios were to enable communities to survive in an area continually hit by drought: they were essentially a cutting edge hydraulic system used to retrieve water from aquifers underground.
"What is clearly evident today is that the puquio system must have been much more developed than it appears today," said Lasaponara. "Exploiting an inexhaustible water supply throughout the year the puquio system contributed to an intensive agriculture of the valleys in one of the most arid places in the world."
Lasaponara adds that "specialised technology" must have been used to construct the puquios. "What is really impressive is the great efforts, organisation and cooperation required for their construction and regular maintenance," she said. "Maintenance was likely based on a collaborative and socially organised system."
The spiral-shaped holes work by funnelling wind into underground canals, wind which then forced water from deep subterranean reservoirs to the places it was needed. Any water left over was then stored in surface pools. The construction was of such a high standard that some of the puquios still function today.
Building something on this scale would have required a comprehensive understanding of the geology of the region as well as the annual variations in water supply, according to Lasaponara.
"The puquios were the most ambitious hydraulic project in the Nasca area and made water available for the whole year, not only for agriculture and irrigation but also for domestic needs," she explained.
Lasaponara is publishing her work later this year in a paper called Ancient Nasca World: New Insights from Science and Archaeology.