East Bay Walls
Coordinates: 38°12′20.32″N 122°57′57.67″W / 38.2056444°N 122.9660194°W
East Bay Walls, also known as the Berkeley Mystery Walls, is a misnomer, as there are many such crude walls throughout the hills surrounding the San Francisco Bay Area. In places, they are up to a meter high and a meter wide and are built without mortar; the walls run in sections anywhere from a few meters to over a half mile long. The rocks used to construct the walls are a variety of sizes. Some are basketball-sized rocks, while others are large sandstone boulders weighing a ton or more. Parts of the wall seem to be just piles of rocks, but in other places it appears the walls were carefully constructed. The exact age of the walls is unknown, but they have an old appearance. Many of the formations have sunk far into the earth, and are often completely overgrown with different plants.
The walls are not continuous and are composed of multiple sections, so they are not fences. They are not tall enough to have been used as defensive barriers. The East Bay Regional Park District simply calls them "rock walls" and notes that they are not mysterious. Livestock, such as cattle, have grazed in the east and south Bay Area hills since the arrival of European settlers. Clearing land of scattered rocks would have eased the ability to move livestock. Placing the rocks into walls would have helped to guide the movement of the animals or to help corral them.
No written documentation exists to identify when they were built, by whom, or why, leading some to consider them to be mysterious.
Some people considered the Ohlone Indians to have been the builders, although they were hunter-gatherers and are not known to have built permanent structures. Some specialists have noted that the walls look similar to structures found in rural Massachusetts, Vermont, and Maine.
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