Here is the dressage arena in last week's snow. The sandy surface was not frozen under the snow, so two circles were cleared for exercising the horses. You can see the smaller of the two, and just part of the larger one curving in front. They were linked, and the smaller one became a turning circle!
I am assuming that human hands cleared the rather beautiful geometric shapes, completed by that little circle right in the middle. Or perhaps aliens who hadn't quite grasped the concept of Earth's seasons took the opportunity to practice their circles.
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