I’ve occasionally stumbled on examples of what are known as the East Bay rock walls or Berkeley mystery walls. No one knows who built them or for what purpose; the consensus is they’re a few hundred years old. “East Bay” and “Berkeley” are actually misnomers: the walls are clustered in numerous locations throughout northern California.
If you Google those terms, e.g., “East Bay rock walls”, etc., you’ll get numerous hits. Drill down, and you’ll get a plethora of speculation regarding the builders of these structures:
- “A heretofore unknown, large scale, and distributed culture”
- Lemurians, survivors of the lost continent of Mu
- Indians wanting to corral a vast lost herd of bison that had wandered in from Colorado
- U.S. soldiers at work during World War 2: the walls were meaningless projects to keep them busy
- Migrant Chinese, perhaps castaways from the great Zheng He fleet of the 15th century
- Chinese laborers of the 19th century who cleared fields to facilitate farming and ranching
- Owners of the Mexican land grants of the early 19th century
- White ranchers who used the walls to corral their cattle
- Ohlone Indians, who used the walls for defense, marking territory, or symbolic purposes
Obviously, some of this crud found on the internet is downright weird. But consider this: when or where else can you, assuming you’re one of several million residents of the San Francisco Bay area, go on a short drive and then walk to and touch artifacts that have generated goofy conspiracy theories and then discuss with your hiking companions which theory is right?
The photo above shows a particularly splendid example of one wall ― which I haven’t visited ― not far from Oakland (California) and thus not far from San Francisco or San Jose and my home.
Alice, my Chorkie, and I encountered another such wall on one of our hikes in Sierra Vista Open Space Preserve in November 2015. It’s shown below.
The overhead perspective below provides abundant clues regarding what this wall is doing here, and we might even extrapolate from my favored theory to explain all of the hundreds(?) of such walls in the grassy foothills of northern California.
I first became mildly interested in the rock walls of northern California, by the way, when one of them presented itself on a residential development project, i.e., an engineering geologic project I was involved with, in San Jose (California).
Click on the link below to read my solution to the mystery of who built this particular rock wall and why. And perhaps all of the prehistoric (i.e., pre-European-settler) rock walls in northern California.