The earth is dug out to create shelters. In most of cases dwellings are dug out in soft soils, tuffs, loess or porous lava in areas with hot and dry climate. Depending on the morphology of the site, the earth is either dug in depth or on a hillside.

The horizontal dug out create caves on the side of the hills, which are accessed by staircases and galleries, such as in China for the school of Fenghuo in the Xiang region.

The vertical dug out are created in areas such as plateaus or plains. A kind of open courtyard is dug out a few meters deep and then room are dug out like caves on the side of this courtyard. Access to the dwelling is done by a staircase, often very steep. Beautiful examples are found in China, in the provinces of Hunnan, Shanxi, and Gansu, where more than 10 million people live in homes dug out of the loess layer. In Tunisia too, one can find interesting achievements.

In Turkey, Cappadocia show exceptional creations where people combined vertical and horizontal dug out.