China’s Great Wall is ‘crumbling.’ Now architects are using drones to save it.

Though it’s often talked about as if it’s a single continuous structure, China’s legendary Great Wall is actually a series of stone fortifications that crawl across the country’s changing landscape from the Korean border to the Gobi desert.

Thousands of miles long and more than 2,000 years old in some places, as much as 30 percent of the wall “lies crumbling into ruins” as it is slowly reclaimed by the natural world, according to National Geographic.