Hartwick Pines Loop is a 7.7 mile loop trail located near Grayling, MI. The trail is primarily used for mountain biking and is accessible from April until October.
Once you find a sign and understand the rectangular shape of the loops, you'll be fine. Signage is minimal but it is definitely marked. I went just before the fall colors typically arrive so I can't speak to the aesthetic of the trail with regards to beauty, but for the most part the trail in wide and mostly flat (although be aware - when the elevation does change, it does drastically!)
Lovely; nice to see the pines and the chapel
Walked a 3rd of the loop. Very peaceful forest trial. Spotted mushroom and a colorful fall walk. Also a very open trail for bikes. It was as if I was the only one there.