by Salvatore Michael Trento
"Ridge-Top Mystery Walls
Berkeley, Oakland Hills, east of San Francisco Bay, California
Ranging along the hills east of San Francisco Bay are long stretches of walls constructed from closely fitted basalt boulders. some of these boulders weigh more than a ton. In a few places, the walls reach five feet in height and three feet in width. They extend far along the hilltops from Berkeley to Fremont, and beyond to San Joes, some 50 miles to the south."
These "walls" can also be found in the area of Mt. Shasta.