You’ve been staring at a volcano all week from your balcony. The white-sand beach, the bright blue water, the crashing waves, and the talented surfers below you on Waikiki Beach should be able to keep your attention. But instead of staring straight ahead, or at least down, your eyes keep turning south to where green Kapi’olani Park abruptly ends and gives way to the volcano’s brown walls. You must hike Diamond Head before you return home.

Some believe Diamond Head State Monument is a volcanic tuff cone, while others call it a vent created by the Ko’olau Volcano. Either way, the 200,000-year-old crater is one of the most recognizable landmarks on not just O’ahu, but in all of Hawai’i. King Kamehameha offered human sacrifices at a temple on Le’ahi’s western slope. British sailors, who thought crystals on the nearby beach were diamonds, gave the crater its English name in the 19th century. Fort Ruger became the first military reservation on the Hawaiian Islands in the early 20th century. Hikers, lots of hikers, now climb the inactive crater each day.

The trail to the Diamond Head ridge isn’t even a mile long, but that doesn’t mean it’s an easy hike. The unpaved path is full of uneven rocks and switchbacks, steep steps and spiral staircases. From the first lookout point, see the eastern side of O’ahu. Dark tunnels continue up the trail. Then pass pillboxes and gun emplacements from World War II en route to the fire control station.

You pause to catch your breath when you reach the summit, yet it’s immediately taken away again when you see the view from the observation deck. You can see Kapi’olani Park—home to the Waikiki Shell amphitheater and the Honolulu Zoo— and Waikiki Beach, where you started. The white Diamond Head Lighthouse is below you. Joggers look like ants along Diamond Head Road, which winds along the crater’s base. Windsurfers and tide pools are on Diamond Head Beach. The south coast of O’ahu and the vast Pacific spread out in front of you. And, since it’s a clear day, you can see Maui and Moloka’i in the distance. The last stop of your trip just became your favorite.