Rivers of fire
Hiking up an active volcano is not an activity for the faint of heart. The rough terrain, the dramatic temperature changes, the hours-long physical activity — oh, and the risk of a volcanic eruption that sends lava flowing down the very mountain you're climbing. But thankfully the latter (usually) carries only a small risk, and the reward of seeing a huge lava lake or lava falling into the ocean is worth the trek.
Lava flows with their glowing, red-and-orange rivers of fire are a breathtaking natural feature to behold — as long as it's from a safe distance. And that experience is possible at these six spots around the globe.