Cave dwellings constitute a unique scene in the cold, dry loess highlands of northwest China that encompass parts of Shanxi, Shaanxi, Henan and Gansu provinces. Earthen slopes there are solid enough to be dug in, in part because rain is scarce.

    Cave dwellings fall into two major types. There are those built by tunneling into an earthen slope. A typical cave dwelling of this kind is a rectangular "tunnel" with a vault-like top and a door and a window at the opening. The "tunnel", so to speak, is up to eight meters deep and three or four meters in width and height. A family may occupy one cave or several standing side by side on the same slope. In some cases, the caves occupied by a family are connected with one another from

inside. If the slope is high and solid enough, the family often has two or more layers of caves dug on it. Buildings are often seen in front of a cave dwelling, which are walled to form a si he yuan-like courtyard.

   There are also "underground cave dwellings" or "underground compounds". In constructing a cave dwelling of this kind, people dig a deep well -- usually seven or eight meters deep and up to 15 meters wide -- on a piece of flatland, and then dig into the walls of the well for space to live in. Meanwhile, flowers are grown in the bottom of the well. "Barking of dogs can be heard but no human being can be seen"- this old saying is a vivid description of those underground compounds.

    Cave dwellings of both types are cost effective in construction while able to afford sufficient comfort all the year round, cool in summer and warm in winter. Poor ventilation and humidity are the chief defects. If not strong enough, cave dwellings may collapse in downpours.