Hershey-owned Mauna Loa provides a self-guided tour of its working factory, where you can watch the humble mac nut as it moves along the assembly line from cracking to roasting to chocolate dipping and packaging. The gift shop sells the finished product at decent prices.
To get here, follow signage about 5 miles south of Hilo; along the 3-mile access road, see acres of macadamia trees.