earthen architecture <p>Buildings and other architectural structures constructed wholly or primarily of earth. For engineering works, such as trenches, created in the earth, use "earthworks (engineering works)." For structures built on a hillside rather than into it, use "hillside architecture." For structures built under the surface of the ground, but not made primarily of earth, use "underground structures.</p> <p>Source: AAT</p> <p><a href="http://vocab.getty.edu/page/aat/300379486">http://vocab.getty.edu/page/aat/300379486</a></p>