medicine wheel in whyoming

what do you guys know about the wheel on the ground made of rocks in whyoming. It has 28 spokes the same amout of days in a lunar month and it aligns with the sun on the summer solstice. in the 1800's when indians were questioned about it they all said it was there before they came.

It's a historic landmark, and one of several wheels:
wyoshpo.state.wy.us...

I've seen various dates for it, but it certainly was made within the last 800 years.

Here's some information on a Native-American listserv. Note that the "carbon dating of the rocks" bit is wrong. You can't carbon date rocks.
nativenet.uthscsa.edu...

Here's an excellent page by a Canadian museum on medicine wheels (there's more than one type!) and a bit of information on how one of them was dated. They all appear to be started around a central carin of stones (which may not have had the outer wheel and spokes added at the same time.):
www.pma.edmonton.ab.ca...