This 10.2-mile trail was part of the route used by ancient Hawaiians to leave offerings at Mauna Loa's summit. Its 7600ft climb is so challenging that when geologist Dr Jaggar hiked it to observe eruptions in 1914, he immediately began lobbying for a new route – hence the Mauna Loa Trail. Access ‘Ainapo (Darkened Land) via private land with advanced permission.

After years of neglect, ‘Ainapo was reconstructed in the early 1990s, somewhat improving a trip naturalist Archibald Menzies, the first European to climb it, famously described in 1794 as 'the most persevering and hazardous struggle that can possibly be conceived.' And he had 100 porters to help him. Excited yet?

You access the trailhead via 8 miles of rough 4WD road across Kapapala Ranch. Call the night before (7:30pm to 8:30pm) for permission, and again in the morning (4:30am to 7am) for the gate combination. If your vehicle can't make the drive, consider splitting the hike over two days and renting Ainapo Cabin ($50, http://camping.ehawaii.gov) at Halewai, 2.7 miles up the trail.