Hiked this during a recent trip to the Big Island. We are avid and experienced California based hikers/backpackers. We've logged lots of time and miles in our local Santa Monica Mountains, Yosemite, Ansel Adams Wilderness, Central Sierra (east and west sides). This Hawaiian Volcanoes Park trail was our first serious hike in the Islands. What an amazing adventure. 11.5 miles RT. Mild 800 foot elevation gain over the hike. The trailhead begins at the Kealakomo parking area (approx. 9.7 miles down the Chain of Craters Road). The first couple miles cross lava flows, slow going, but well marked with lava cairns. The trail next follows the former Chain of Craters road (you walk along old, lava covered pavement), before entering a forest area that transitions to much denser rain forest. The trail intersects the Napau Trial 3.2 miles from the Naulu Trail trailhead. Turning right at the intersection takes you past the eastern end of the Makaopuhi Crater with good views into that crater, through more very dense rain forest, past the ruins of a former pulu factory (amazing on its own), and past steam vents literally right next to the trail, to the Napau Crater overlook with Pu'u O'o steaming in the distance about 2 miles away. We spent over an hour just hanging out at the overlook letting the day pass by. A moderate to challenging hike depending on your condition. We loved every bit of it. The weather cooperated completely. Nary a drop of rain. And most amazingly, no bugs of any sort, not biting, buzzing, nothing!! A totally new environment for us. Orders of magnitude more enjoyable and interesting for us versus the apparently more popular and well known/worn Kilauea Iki trail. We met one other hiker early in this hike, then had it to ourselves the rest of the day. Highly recommended for a serious, day long hike into an area of great diversity, interest, and solitude.