Hawaii Volcanoes National Park
Watching an actual volcano in action is a far cry from the baking soda science experiments kids do at school. At this Hawaiian park, visitors watch—at a safe distance—as hot lava spills into the Pacific, where it bursts into particles later pulverized by the waves into black sand. The park is home to two of the world's most active volcanoes, and rangers will bring you down into the lava tubes (subterranean caverns formed by hardened molten rock) and maybe even play you a tune on a ohe hano ihu, aka the Hawaiian nose flute. Says reader Angela: The surreal black landscape is "one of the few places in the world where your kids can stand on earth that is younger than they are." One Crater Rim Dr., 808/985-6000, nps.gov/havo. Park entrance fee is $10 per vehicle; bike or foot entrance starts at $5.