Most weekdays, she leaves home around 8 am, carrying water and a packed lunch. She follows the line of the Great Wall through the mountains until mid-afternoon, returning home as the sun dips behind the ridges. A phone app tracks her steps: about 20,000 a day.

Her duties include picking up trash, checking the masonry for loose bricks or new cracks, and reporting damage for repairs.

Another critical part of the job is intercepting "wild hikers" attempting to climb undeveloped sections of the Wall.

Stretching roughly 21,200 km across northern China, the Great Wall spans 15 provinces and regions. More than 520 km run through Beijing alone, crossing six districts and including some of the best-preserved stretches of the Ming-era section. Among them is Badaling, the most visited section and part of the UNESCO World Heritage Site.

Yet in Beijing, only about 5 percent of the Wall has been restored and opened to visitors. Much of the rest remains in fragile ruins, exposed to natural erosion and the pressures of unauthorized climbing.

In Shixia, none of the Great Wall is officially open to the public. The scenery is striking: steep mountain paths winding through dense forests. But loose stones and sheer slopes make the terrain hazardous.

During her patrols, Liu often encounters hikers who have slipped past warning signs and barriers. One incident still stands out.

Three summers ago, she came across a family tour group. A child in the group had picked up fragments of white mortar and begun drawing on the ancient bricks.

"I hurried over and asked the child to stop," Liu recalls. She then asked the guide to show identification. The guide said he had none and questioned how Liu could prove the child was responsible.

Liu answered firmly.

"The Great Wall is a heritage left to us by our ancestors," Liu says she told him. "It doesn't belong only to our village; it belongs to everyone."

The guide eventually apologized. Later, Liu and a colleague wiped away the marks with handkerchiefs and wet tissues.