This loop formed by the Kilauea Iki Trail and Crater Rim Trail is one of the most popular and most beautiful in Hawaii Volcanoes National Park. The main draw is the ability to cross a now-dried lava flow in a volcanic crater. As you hike across the fractured black rock surface, you'll spot steam vents hissing along the trail, indicating just how active the volcano still is beneath your feet. The most recent eruption was in 1959—who knows when the next one will be?!