After centuries of neglect, the world's largest fortification, the Great Wall of China, has a band of modern-day defenders who are drawing up plans to protect and maintain the vast structure.
They're not a minute too soon: Roughly a third of the wall's 12,000 miles has crumbled to dust, and saving what's left of it may be the world's greatest challenge in cultural preservation.
Qiao Guohua is on the front line of this battle. He lives in the village of Jielingkou, not far from where the eastern end of the Great Wall runs into the Yellow Sea.
During the Ming Dynasty (1368-1644), Jielingkou was a walled garrison for soldiers guarding the wall at a strategic pass.
It's now a simple farming village of some 800 residents. Other sections of the Great Wall were built during the Qin Dynasty (221-206 B.C.) or earlier.
When not tending his crops, Qiao patrols a 5-mile stretch of the wall, looking for and reporting to the government sections in danger of collapsing — and tourists who might want to make off with a brick or two as a souvenir.
"Every stretch of this wall was built with the blood and sweat of the working people," he says. "After I tell folks how many people died building it, they begin to get in the habit of protecting the wall."
Qiao says he's certainly not doing this for the money — the local government pays him a mostly symbolic sum of $150 a year for his labors. Just recently it also issued him an imitation military jacket that says "antiquities protector" on the back in Chinese — and "U.S. Army" on the front.
He walks along his section of the wall in all four seasons. He knows intimately every feature: all 10 towers that rise above the wall, and the snakes, hares and other wildlife that inhabit the area.
For nearly two millennia, until the 1600s, the wall marked the frontier separating the agriculture-based civilization of China from the nomadic peoples of the Eurasian steppe, including the Mongols, Manchus and Xiongnu. The wall was designed not so much to keep the peoples apart as to regulate their commerce and interactions.
Qiao says the wall is still a sort of internal dividing line. He points to the north.
"On that side is a Manchu autonomous county," he says. "On this side are ethnic Han people. Over there, they bury their dead. On this side, we cremate ours. The policies are different."
As an ethnic minority, Qiao adds, the Manchus are exempted from the family planning policies that the Han face.
Qiao says that when he was a child, the wall's towers and battlements, made of brick more than 400 years ago, were still in excellent condition.
But during the 1970s, under Chairman Mao and the Cultural Revolution, officials encouraged people to dismantle the wall and use the bricks to build their own homes.
Qiao points to a large stone built into the wall of one village home.
"You don't see these stones anywhere else," he says. "It's ancient. See that? That piece was taken from the wall."
In another village not far away lives a man named Xu Guohua. He grew up playing on the Great Wall.
A few years ago, he discovered more than 200 large kilns in which bricks that were used to make the Great Wall were baked. Xu has opened a museum full of Great Wall artifacts he's discovered. And he's found something else: a personal connection to the Great Wall.
One summer not long ago, a stretch of the wall near his home collapsed. In the rubble, Xu found a stone tablet. He uses a towel to wipe dust off the 4-foot-long slate-gray slab, revealing several carved Chinese characters.
Xu says the tablet confirms what is written in his family's genealogy: that a 17th century ancestor was an official who helped build this section of the wall.
"After four centuries, we descendants are still connected to him," Xu says. "We are still watching over the Great Wall and protecting it."
Standing on the Great Wall above Xu's museum, I talk to Dong Yaohui, vice chairman of a civic group called the China Great Wall Society. He has just finished a multivolume compendium of local histories of the Great Wall.
The section of the wall we're on is in comparatively good condition, its parapets and towers largely intact. Dong says that roughly 10 percent of the wall is well-preserved.
But he estimates that a third has vanished completely, and that the remaining 60 percent is in various degrees of disrepair. Most of that is from natural erosion, but development projects also have damaged the wall, or even replaced parts of it with gussied-up replicas.
The job of saving what remains of the wall is too big a task for China's government alone, Dong says. China has enacted regulations to protect the wall, but many local governments are in impoverished areas and can't pay to maintain it. Dong's plan is to get companies and individuals to sponsor sections of the wall.
"See these bricks in the wall? Each one is very ordinary, but together in large numbers, they make a magnificent wall," he says. "Protecting the wall is the same idea. Each person or company we get to contribute to the effort is like a brick."
Dong recently launched pilot sponsorship programs; the money will be used to pay local communities and governments to patrol and repair the wall. He envisions planting markers along the wall with information about each particular section's history and sponsors, and is pressing China's national government to adopt his sponsorship plan nationwide.
In the 1980s, Dong and two companions became the first Chinese to walk a 4,300-mile Ming dynasty section of the Great Wall, east to west, using more than 500 days to document its condition and the landscapes and communities along it.
"The Great Wall was constructed and defended in separate sections," he notes. "Nobody has left his or her footprints across the whole thing. I thought it would be a very exciting thing to be the first human being to do this."
Three decades after his own trek, Dong encourages students to follow in his footsteps, embarking on journeys of discovery and learning along the Great Wall.