Climb to the top of Castle Rock for a breathtaking view of the Straits. Castle Rock is a limestone rock formation that stands nearly 200 feet above the ground. This activity offers exercise and some great photo opportunities, plus it doesn't cost very much! (I think it's less than a dollar to climb it.)
Also, just for kicks and cheesy fun - there is a statue of Paul Bunyan and Babe the Ox at the base of Castle Rock. How many people can say they've had their picture with Paul Bunyan?
Castle Rock can be found in St. Ignace on business loop I-75. There are also some great roadside parks/scenic turnouts along this stretch.
The Headlands is a beautiful county park spanning 550 acres along the Lake Michigan shoreline. There are nice nature trails filled with wildlife and plants for hiking or bicycling. One tip - bring bug spray!