Mauna Loa Macadamia Nut Visitor Center Keaau HI The is the largest macadamia nut producer in the world. It is located just outside Hilo, Hundreds of rows of macadamia nut trees line Macadamia Road on the three mile drive leading to the visitor center and processing plant. At the visitor center there is a garden to stroll through. This is a plumeria. Pink hibiscus. Red hibiscus. Tiger lily. Red ginger.