This 7-mile (one-way) undulating hike over rugged terrain begins with the excellent Mauna Ulu Eruption Trail before continuing across acres of pahoehoe (smooth-flowing lava) to the edge of the mile-long Makaopuhi Crater . There it heads into the muddy fern forest past the Old Pulu Factory to the edge of Napau Crater with Puʻu ʻOʻo steaming silently on the horizon.
We have a love-hate relationship with this trail which can be grueling at times, but pays big dividends in terms of diversity and views. Self-register at the trailhead off Crater Rim Dr for day trips beyond Puʻu Huluhulu . To overnight you'll need a permit ($10) from the Backcountry Office , where you can also ask about trail conditions and closures in this geologically unstable area. The small official camping area has no view and no water; skip it if you can manage the 14-mile round-trip in a day. You can shave off about 4 miles if you start on the Naulu Trail from Kealakomo on Chain of Craters Rd. However, it's a rough uphill hike and you'll miss the grand views and huffing vents along Mauna Ulu's flank.
