Beijing's Forbidden City was built using incredibly heavy stones that had to be hauled down long-windy ice roads; so how did they do it?
Records of the city's construction in the year 1406 suggest the stones were transported using wooden sledges, which are believed to be more effective than rollers and other common methods of the time, Nature reported.
The stones were transported from a quarry about 43 miles (70 kilometers) away.
"You go to the Forbidden City and see these massive rocks, and you ask yourself: 'How in the world did they ever move this rock here?'" Howard Stone, a fluid mechanicist at Princeton University, said.
The "Large Stone Carving", a major tourist attraction in the Forbidden City, weighs 300 tons. The statue is 55 feet long, 10 feet wide, and three feet thick, the National Geographic reported.
Historians have suggested that teams of men pulling sledges were used to move the monstrous rocks, but this is the first time a detailed account of the process has been uncovered, Nature reported.
Jiang Li, a mechanical engineer at the University of Science and Technology Beijing found a record of the transportation of a 112 ton stone slab. The endeavor occurred in the year 1557, and it took four weeks to complete. This means the stone was moved about three inches per second.
Li believes the transportation teams used sledges instead of wheeled vehicles simply because the burden was too heavy for those vessels to bear.
An "ice highway" was created between the quarry and city, and was used as a transport route, National Geographic reported. The ground was believed to be lubricated with water from wells as the stones were moved along.
"Some people have asked if the wells are still there. It would be interesting to look for them," Princeton engineer Howard Stone said.
Each stone was pulled by about 43 men, and sometimes they were even required to cross rivers.
"I'm not surprised. If you get enough people, enough rope, and enough time, you can move just about anything," archaeologist Charles Faulkner of the University of Tennessee, Knoxville, who was not on the study team. "And they had a lot of time. And a lot of people."
