Honolulu, HI, United States
One of the most famous volcanic craters in the world, Diamond Head overlooks Oahu's southeastern shores. The crater was originally named "Laeahi" because its silhouette resembles the "brow of the tuna." British sailors gave it its current name upon arrival on Oahu's shores because the calcite crystals on the crater glistened in the sunlight from a distance. They mistakenly thought there might be diamonds in the mountain. The crater is over 3,500 feet in diameter, and visitors can climb to the 760-foot summit. The observation deck was constructed at the summit in 1910 to provide military target sightings. The trail is paved almost the entire way but can be steep in spots. Be sure to wear sunscreen and bring water on the hike, as there is no fountain up top.