Sinkholes Pathway is a 2.4 mile loop trail located near Onaway, Michigan and is good for all skill levels. The trail is primarily used for hiking and is accessible from April until November.
Short, easy hike around 2 - 5 sinkholes. I last visited these in 1966, when the trees in them were much smaller. Now, they are heavily forested so it's harder to tell exactly what they are. But it's a pleasant hike on an extremely well marked trail. Approx 2.2 mile loop though there's a shorter option. Worthwhile if you're in the area.