DaBus (city bus) over, and discovered that it's a hike just to get from the main road to the visitors' center in the crater. The Waikiki Trolley goes directly to the visitors' center, though, so I was able to save myself some walking in the afternoon and took that back to the hotel.
Anyway, that hike up Diamond Head is a doozy. It starts out with a paved footpath, which gives way to dirt and gravel, and eventually turns into a mule track capped off by sets of stairs tunneling through the rock. I emerged in a concrete bunker on rim of the extinct caldera, then clambered through a window. The reward is cool breezes and an iconic view of Waikiki. My timing was lucky because as I looked out over the Pacific, the aircraft carrier Carl Vinson was heading east to San Diego. I chatted with a kid from Texas who proposed that we build a water slide along the inside of the crater to save us the hike back down.
I ended my day, and my stay in Waikiki, by snacking on Lilo & Stitch-branded Hawaiian Host chocolate-covered macadamia nuts from the ABC Store, while watching "Lilo & Stitch." After sunset there were fireworks next door at the Hilton Hawaiian Village (every Friday night at 7:45).
Ah dear Waikiki How I have come to love thee.