[protest1]

sorry posted twice by mistake!

[djf]

Certainly many are man made. But there have been more than a few that are so large, it defies explanation as to how it could have been done. A surveyor type/civil engineer was quoted after seeing one of the biggest and most complex circles ever made that it would take a team of twenty men, with all the modern tools and instrumentation they could get, two weeks of full time work to make the circle.