Petroglyphs

The petroglyphs, carved into sandstone by American Indians, are only available for viewing on Fridays, Saturdays, and Sundays. Fortunately there was a guide there today who showed us the carvings and explained their stories. Fascinating!
http://en.wikipedia.org/wiki/Sanilac_Petroglyphs_Historic_State_Park

There's a marked trail through the park.

Some photos, which can be enlarged by clicking on them, from along the way: -

I crossed the river twice on swaying bridges. Both times I saw bull head water lilies.

A 125 year old triple trunk white pine tree that grew after the last great fire in the thumb.

The sandstone must be protected from the elements because erosion can quickly erase the images uncovered during the last fire. Vandals removed some of the glyphs probably about 100+ years ago. Moss is growing on the stone now; they could also destroy the carvings. Ideally the sandstone should be protected by a fully enclosed all-weather building.