When the island of Kauai erupted from the sea between 4 and 5 million years ago, parts of the coastline were riddled with tubes where molten lava once flowed. One of those spots is the Spouting Horn on the island’s southern coast, where waves are channeled into the tube before violently erupting in a saltwater geyser over 50 feet in the air. Compared to other Hawaiian blowholes, what makes Kauai’s Spouting Horn unique is the guttural moan that precedes the powerful eruption. A second, smaller hole in the rocks funnels air as opposed to water, and the result is a sound that makes it seem like the rocks themselves are groaning. No wonder Hawaiians believed that a mo’o was stuck inside of the rocks—a mischievous lizard of Polynesian lore that can still be heard to this day. Once finished admiring the geyser and feeling the ocean’s fury, peruse the homemade souvenir stalls erected by local vendors. Even if you don’t find that perfect give to bring back from your Hawaiian vacation, the locals are always a good source of friendly conversation.