An elderly woman sits in front of her underground dwelling in Pinglu, Shanxi province. [Photo by Liu Wenli and Sun Ruisheng/China Daily]

Wang was named an intangible cultural heritage expert by the provincial authority in 2008 because he is one of the few today who knows how to build the dwellings.

Wang says the dwellings are not that difficult to build but "expensive to maintain".

To create the dwelling, a pit covering an area of about 200 square meters and 7 to 8 meters deep, is dug on a flat and thick loess plateau, with a spot carefully chosen by feng shui masters as its center. The bottom of the pit is the courtyard, and arched caves are then dug on the sides of the pit, forming rooms.

A winding corridor leading to the bottom of the pit is dug as the only way to enter and leave the residence. But the entrance of the corridor is always hidden to keep possible intruders out.

In the courtyard there is a well, which also collects rain for daily use, and a wastewater soak pit.

On the flat roof of the dwelling are two stone rollers.

Wang says he uses the rollers to roll the earth to make it compact and solid. The grass growing on the top of the platform must be removed as the roots can damage the soil layer.

If maintenance is not done in a timely fashion, the loess can become loose and the arched caves will collapse.

Besides treating livestock in nearby villages, Wang spends most of his time mending and reinforcing his home.