4. Haleakala National Park.
Every year, more than a million tourists visit Haleakala National Park, home to the world’s largest dormant volcano. Haleakala’s summit stands more than 10,000 feet above sea level (in fact, you can see it from any point on the island). Once you reach the top of Haleakala, you can keep going down into the mouth of the volcano. The Haleakala Crater measures 19 square miles and offers a stark glimpse into Hawaii’s early beginnings.