One of Costa Rica's seven active volcanos, Arenal is also one of the world's most regularly active volcanoes. Since its famous eruption in 1968 that wiped out a small town, Arenal's frequent explosions send red-hot lava rocks tumbling down the volcano's steep slopes, day and night. If you are lucky enough to visit on a clear night, which is not always the norm-- you'll see to the top, and the night sky turned red by lava spewing from Arenal's crater. In the past few years, the forests to the south of the volcano have been declared Arenal National Park, which will likely stretch to meet Monteverde Biological Cloud Forest Reserve. The small town at the base of the volcano is a charming place to stay and soak up some local culture, and soak in some natural hotsprings.