I was just looking at the stonework pics in this thread. I am a master dry-stone mason. I have been all over america doing this specialty and studed under some of the words best. The stonework in the pic is held together by gravity and friction. As is all dry-stone work. I moved a hot-tub full of water and still on the deck, around a house by myself and with only rollers and levers. I built a solar home for myself years ago and the orientation had to be 15 degrees north of due east. To make such a percise angle I waited until the fall equanox. I drove a stick in the ground and at sunrise placed another lining both up with the rising sun. I waited until sunset and checked my alinement and yes it was the same. On 2 days out of the year the sun rises and sets due east and west.I now had an exact east-west line. By dividing the number of days in a year,365 , by 3.12, I had the radius of a circle in witch each foot equaled 1 degree . So I drew a circle with a string on my line, measured 15 feet(degrees) to the north and there was my alinement. No aliens needed, just a string and an understanding of math and astrominy. We underestimate the brains and skill of our ancesters.