Arrive early to avoid the tour buses at the Thurston Lava Tube, a.k.a. Nahuku, an attraction that delivers the scenic goods on the rim of Kilauea Caldera in Hawaii Volcanoes National Park. The wide path begins down a bird-rich, ohia-and-tree-fern forest, a lushly set songfest you would not expect to experience so close to the barren lava of an active volcano.
The tube, lit by lights, has a dripping ceiling about 15 feet high, like a subway tunnel sans train. Lava tubes are formed when the surface of fast moving lava cools and hardens. The hot lava continues to flow underneath until the source ceases, and the tube drains. This underground passage is nearly a quarter mile long—with an option to continue another 1,000 feet if you have your own flashlight and don't get creeped out.
Full directions on how to get there and several crater hikes in the vicinity can be found in the Hawaii the Big Island Trailblazer guidebook.