I posted back in early September about visiting "America's Stonehenge" in Salem, New Hampshire while on vacation. While it seems to be laid out on astronomical principles, it is by no means a tremendous engineering feat like the real Stonehenge on the plains of Wiltshire in England.
There have been many attempts to figure out how the stones in Wiltshire were transported and erected. This "Discovery Channel" article describes some theories and tests.
A fellow in Michigan named Wally Wallington has studied this and has shown how large stones can be moved and erected using the brains and brawn of one person without any machinery. The YouTube video is at http://j-walkblog.com/index.php?/weblog/posts/moving_big_rocks/. The description of the video says:
Wally Wallington has demonstrated that he can lift a Stonehenge-sized pillar weighing 22,000 lbs and moved a barn over 300 ft. What makes this so special is that he does it using only himself, gravity, and his incredible ingenuity.Watch the video - it's pretty amazing. The key seems to be small rocks!