What is it like to live in a cave once inhabited by ancient civilizations? Zhang Youbin and his wife have the answer.

Squatting on the ground, using a lighter to ignite a pile of leaves, 44-year-old Zhang is ready to fix lunch in the cave, which is not very big and is located deep in the mountains, about a two-hour drive from Zhenfeng county, Southwest China's Guizhou province.

Zhang is from a village in Zhenfeng. Six years ago, the local government entrusted Zhang and his wife with the care of the ancient Hongyan cliff paintings, which decorate the cave.

The cliff paintings were first noticed in 1991 and have a history of more than 6,000 years, according to Li Wenxin, director of the county's heritage administration.

In 2015, the area was listed as a provincial-level protection site. The paintings cover a cliff area of 110 meters in width and 0.5 to 20 meters in height. Most patterns have become blurred over the years. Those still recognizable show cows, palm prints, pigs and people.

"It is suspected that the paint is cinnabar," Li says, adding that the paintings are specific and have certain artistic and ornamental value.

"In particular the porcine patterns, which were first found in the surrounding areas along the Beipan River, indicating high research value," he adds.

In 2015, the couple settled there to protect the paintings.

The road leading to the site was extremely narrow and dangerous in some sections. Visitors needed to lean tightly into the cliff to pass them. Due to that, Zhang was determined to widen the road. It took him two months to dig using hoes and build the roadbed with stones.

"The road is now much easier for people to walk on," he says.

The couple's principal responsibility is preventing those without authorization from entering the protected area in case the paintings are damaged.

"My wife and I take turns guarding the paintings every day, rain or shine," Zhang says.