Colorfully named Le'ahi (brow of the ahi tuna) by native Hawaiians, Diamond Head is a misnomer coined in the early 1800s by British sailors who mistakenly thought local calcite crystals found here were sparkling diamonds. Starting from the trailhead on Diamond Head Road, if you tough out the 1.4 mile hike, you'll find that the hidden treasure is actually an incredible 360-degree view of the city of Honolulu, the Ko'olau mountains, and the surrounding coastline from here.