mistério nos eua

In the hills around East Bay and elsewhere near San Francisco, there is a series of stone walls that extend discontinuously for miles.There is no record of them being built or who might have built them. Some interested investigators have suggested exotic explanations for them such as that they were built by the Chinese, the Mongolians, or even refugees from Mu or Lemuria. Others have suggested that they were built by Native Americans or early European settlers with the help of Native American or foreign laborers. So what is the truth behind these mysterious walls?