Millions of houses around the world are actually made from earth in one form or another, but the technique of cob building is vernacular to many parts of the UK. In Devon, even today, you can still find many buildings that have been standing for hundreds of years, made from local cob.
The advantages of cob is that it is usually local (often dug up from a few feet away), simple to make, highly sculptural and provides a lot of thermal mass. The downside is that construction can be slow (unless there's a large group of helpers!), and cob itself does not provide much in the way of insulation.
Anyway, pros and cons aside, cob buildings can be some of the most beautiful structures around. Hat-tip to Steven Golemboski-Byrne who had a link to this building in Somerset on his blog.