Nearly 4,000 miles long, the Yangtze has watered civilizations for millennia—and laid waste to them too. The eighth-century poet Li Bai wrote that navigating the river was "even harder than ...

When reviewing the photos, he saw something he hadn’t noticed before: A mountain shaped like a dog’s head rested on the ground next to the Yangtze River, its snout perched at the water’s edge.