Kona Coffee Belt
Kona coffee (grown in the volcanic soil of the Kona Coffee Belt between 800–2,000ft on Mauna Loa's slopes) is among the rarest and most prized coffee in the world — the only commercial coffee grown in the US. Greenwell Farms is the best free farm tour on the island: 45–60 minutes with a knowledgeable guide covering the full process from cherry to cup, including a cupping at the end. Bay View Farm is shorter but convenient if combining with Puʻuhonua o Hōnaunau nearby. Critical reminder for buying: Hawaii law allows "Kona blend" coffee to contain as little as 10% actual Kona beans. Buy only 100% Kona from the farm directly — never from airport shops.
Greenwell Farms: free guided tour offered daily 9am–3pm (arrive 15 min early); at 81-6581 Mamalahoa Hwy, Kealakekua — ~20 min from Kona. Bay View Farm: free guided tour (~30 min) daily 10am–3pm; at 83-5980 Painted Church Rd, Honaunau — ~30 min from Kona. No reservation required for either; paid tastings available.
Open year-round. Outdoor tour through working coffee trees — best when trees are in cherry (fruit) October through February.