XI'AN -- "Cave houses" have become a top choice for tourists in Yan'an, a former revolutionary base of the Communist Party of China (CPC).

"In addition to their distinctive appearance, the facilities inside are modern. I can take a hot bath and have access to the internet," said tourist Cheng Shangzhi.

A cave house, or "yaodong," is a form of earth shelter dwelling common on the Loess Plateau in northern China. Taking advantage of thick loess layers and favorable landforms, the sturdy and durable yaodongs are mostly carved into hillsides. They do not take up valuable arable land and are warm in the winter and cool in the summer.

Earthy caves were once considered a symbol of poverty. But in 2019, Yan'an put an end to absolute poverty. Although China is undergoing earth-shaking changes, cave dwellings -- one of the earliest dwelling types of human beings -- are still found all over the Loess Plateau.

American journalist Edgar Snow wrote about the unique dwellings when he first visited Yan'an in 1936. He penned the classic "Red Star Over China," which gave a rare, detailed and brilliant account of the Chinese revolution in the 1930s.

Edgar depicted a Red Army university that "was probably the world's only seat of 'higher learning' whose classrooms were bombproof caves, with chairs and desks of stone and brick, and blackboards and walls of limestone and clay."

In the process of the Chinese revolution, Yan'an cave dwellings played an important role. One night in 1935, exhausted Red Army soldiers arrived in Wuqi county of Yan'an. Mao Zedong spent the night in the cave of local villager Zhang Ruisheng.

"Chairman Mao arrived at my house at around 7 or 8 in the evening. My family prepared mutton and buckwheat noodles. The chairman praised my father, said he did a good job in cooking," said Zhang.

Under the arched roof, Mao and his comrades reorganized the Red Army, beginning a 13-year-long revolution that led to the founding of the People's Republic of China in 1949.

Xu Junfu has been living in caves all his life in Kangping village, located in the Fengzhuang township of Yan'an's Baota district.

"Primitive earthy caves were humid and would easily tumble down. But the stone cave in which I'm staying today is safe and sturdy, and can offer shelter for at least 300 more years," said Xu.

Statistics show that over the past decade, more than half of the 1.5 million rural residents of Yan'an have moved into new cave houses built with stones.

Since 2018, vacant caves in the village have been gathered under unified management. Distinctive cave hotels offer a unique experience for tourists eager to get a taste of the traditional dwellings and reminisce on the CPC's history.

Higher-quality and moisture-resistant materials, modern furniture, electric appliances, spacious rooms with plenty of daylight, and improvements to the natural environment brought by afforestation mean cave hotels are not a painful experience for tourists recalling tough revolutionary days.

Each household in the village earns an annual average of nearly 10,000 yuan (about 1,540 U.S. dollars) by renting their vacant caves to tourism cooperatives. Villagers have become service providers, taking on jobs such as tour guide, housekeeper and store owner.

Despite the COVID-19 epidemic, the per capita annual income of villagers in Kangping exceeded 17,000 yuan last year, higher than the level seen in 2019, according to the local government.

"The 'Golden Week' May Day holiday is approaching. The cave hotels in the village are set to embrace a tourism peak. This year's tourism income will definitely return to the pre-epidemic level," said Bai Xijun, deputy Party head of Fengzhuang.