Science Frontiers:
R. Swanson researched the "rock walls" in the East San Francisco Bay area as reported in 1985 by William Corliss.
http://www.science-frontiers.com/sf038/sf038p01.htm
http://www.science-frontiers.com/sf039/sf039p01.htm
The following article was liberated without permission from the William Corliss' book 'Ancient Infrastructure: Remarkable Roads, Mines, Walls, Mounds, Stone Circles'.
Mr. Corliss' books can be purchased through the Science Frontiers website, Amazon and elsewhere. If you enjoy reading about the curious, unusual, or the unexplained, his books are a great read. Included in Mr. Corliss' books is information on many other rock structures that academia has failed to explain.