The loess, which is as deep as 100 meters, is extremely difficult to penetrate water and has a strong verticality, which provides a good premise for the development of caves. At the same time, natural conditions such as dry climate, cold winter and less wood also create opportunities for the development and continuation of caves that are warm in winter and cool in summer, very economical and do not need wood. Due to the influence of natural environment, landform and local customs, caves have formed various forms. But judging from the layout and structural form of the building, it can be divided into three forms: leaning on the cliff, sinking and independent.
The caves in Yan 'an, northern Shaanxi are mixed with cave-style flat-roofed houses. Cave dwelling is an organic combination of natural landscape and life landscape, which permeates people's love and attachment to the yellow land.
Cliff cave (cliff cave)
Cliff-leaning caves include mountain-leaning caves and ditch-leaning caves, which are often arranged in curves or broken lines, with harmonious and beautiful architectural artistic effects. When the height of the hillside allows, sometimes several terraced caves are arranged, which are similar to buildings.
Sinking cave (underground kiln)
Sinks are underground caves, mainly distributed in the Loess Plateau-areas where there are no slopes and ditch walls to use. The practice of this kind of cave dwelling is: first dig a square pit on the spot, and then go to the cave dwelling with four walls to form a quadrangle. On the flat land, people can only see the treetops of the courtyard, but not the houses.
Independent cave (ring kiln)
Independent cave dwelling is a kind of arched house covered with soil, including adobe arch cave dwelling and brick arch cave dwelling. This kind of cave does not need to be close to the mountain and cliff, and it can be independent without losing the advantages of the cave. It can be a single story or a building. If the upper floor is also a hoop kiln, it is called "kiln on kiln"; If the upper floor is a wooden house, it is called a "kiln house".
The cave is fire-proof and sound-proof, warm in winter and cool in summer, which saves land, labor and economy. It is indeed a perfect architectural form adapted to local conditions.