The iconic silhouette of Diamond Head State Monument can be found along the Honolulu skyline, just beyond Waikīkī. This 760-foot tuff crater is a famous Hawaiian landmark and is known as Lē‘ahi in Hawaiian, meaning the "brow of the tuna." The crater was named Lē‘ahi Head by 19th-century British sailors who thought they had discovered diamonds on its slopes, but they were shiny calcite crystals. The crater has a rich history, including being used as a military lookout in the early 1900s and becoming a National Natural Landmark in 1968. Today, it is a popular hiking destination offering breathtaking views of Waikīkī and the south shore of O‘ahu. The hike is moderately challenging and includes two sets of stairs, tunnels and old military bunkers. The Diamond Head State Monument is open daily from 6 a.m. to 6 p.m. with a $10 admission fee per vehicle and $5 per pedestrian.