Its spectacular location in the Peruvian Andes has made Machu Picchu a magnet for trekkers and selfie-seekers but puzzled generations of archaeologists.
Now a geologist claims to have solved the mystery, saying the ruined city owes its position atop a narrow ridge at 7,970ft (2,430m) to a series of faultlines that created its building materials.
Machu Picchu was constructed in the 1400s only 46 miles from the historical Inca capital of Cusco yet so remote that it was not discovered by the conquistadors. The site, which may have been a sacred centre, a royal citadel or both, has buildings with mortar-free masonry so fine that it is impossible to slide a credit card between the huge stone blocks.
Rualdo Menegat, of the Federal University of