Once verdant agricultural land, the National Park of Timanfaya is now a barren series of volcanic lava fields thanks to devastating volcanic eruptions in 1730 and 1824 that laid waste to the area. Declared a UNESCO World Biosphere Reserve in 1993, the lunar landscape is popular with visitors, who tour the area by bus (in around 45 minutes) or on foot. Free guided tours (ages 16 and over only) in English or Spanish should be booked in advance and take in the martian interior's barren landscapes or the coastline of the park as it is slowly recolonized by plantlife. You can even take a tour on the back of a camel if that's your thing.