Following the Appalachian Trail leave Unicoi Gap and run up and over Rocky Mountain, cross Indian Grave Gap, climb to the top of Tray Mountain and return to Unicoi Gap all via the AT.  It's a technical and rocky effort that's fairly popular for local trail runners along the AT. The route has a Strava segment.

https://www.co.jackson.mi.us/1218/Falling-Waters-Trail

Connecting the Village of Concord with the City of Jackson, the trail was built on an abandoned stretch of the Michigan Central Railroad. The 10.5-mile, 12-foot-wide paved trail is ideal for walking, running, or biking. As it travels through natural springs and lakes that form the headwaters of four major Michigan rivers.