5) Berkeley Mystery Walls, Berkeley
Spanning 50 miles across the East Bay of San Francisco from Berkeley to San Jose are the Berkeley Mystery Walls. Why so mysterious you might ask? Because no one has any idea who built them! Boulders and other rock formations are up to five feet high in some places. Some are in ruins, while others are intact weighing over a ton each. Others run as long as a mile in length. The stones were originally discovered by Spanish settlers in the Bay Area, who noted they had no clue how they got there. Historians and scientists have studied them and there is no conclusive evidence as to who built them or what their purpose was. Some speculate the wall may have been built by Mongolian settlers, but there’s no dating proof accurate enough to draw a firm conclusion.
