From a Michigan.org online article:
There are over 140 miles of trails and roads leading to great views on Mackinac Island. Stop by the Visitor’s Center to buy a map of the trails, significant points of interest and self-tours. Or visit a rental bike shop for a map, (though these have less detail). One of the most popular trails is the 8.2-mile road along the island’s perimeter. Typically there are bikers along this trail, but plenty of pedestrians also use it to see the beautiful shorelines. The road is not very hilly but it is long, so take your time to enjoy the views and be sure to stop occasionally to read about the history of the island. If you’d like to get deeper inland, there are several trails that lead to great views of the changing reds, yellows, and oranges as well as vantage points to see the beautiful shorelines. Stay aware of bikers and horses and be sure to stop at Sugar Loaf, Fort Mackinac, Skull Cave or Arch Rock for amazing views.