Maui is known as the "Valley Isle" for - you guessed it - lotsa valleys. Its geography is unique in that it was formed by two volcanoes that merged to create an uber volcano that geologists like to call a "volcanic doublet." Whale-watching fans can spy humpback whales, an endangered species, during the winter months. A popular tourist activity is driving the Hana Highway along the east coast of the island. It's a windy adventure through black sand beaches and waterfalls but worth it for the scenic beauty. Just don't drive too fast or locals may yell "slow down, mainlander!" Other hotspots are the town of Lahaina, Kaanapali, and Haleakala National Park.