Iao (rhymes with "meow") Valley State Park is on Maui's tour-bus circuit, and its signature feature, the Needle, is an easy walk on a paved path. Shutterbugs go wild. Still, the place delivers the scenic goods and is a sure thing for visitors: In addition the Needle-viewing platform, families can bag a botanical garden and take another short trail up the stream and envision where, in 1790, the invading forces of Kamehameha the Great from the Big Island drove Maui's warriors into a slaughter, their fallen bodies actually blocking the flow of the stream and creating its subsequent name, Kepaniwai, "damming of the waters." (Only a handful of the Maui guys escaped, via a treacherous trail that pops out on the other side of the island at Olowalu Valley; see page 58 of Maui Trailblazer.)
On the way to the state park, which is only two miles from county seat of Wailuku, are two other noteworthy stopovers: Tropical Gardens of Maui, with a 25-year growing history, features a bridge over the stream and a cheap ($5) entry fee. And, about a mile before road's end is Kepaniwai Heritage Gardens, a family freebie, with banyans, coco palms and other tropical flora surrounding replicated structures that represent the main cultural threads of Hawaii's history: Polynesians, Chinese, Japanese, New England, and Filipino—the whole calabash.
The hot tip for adventurers is the short trail that leads from the Iao Needle viewing pavilion at the state park. Hop the rail and follow a well-worn trail up the valley (the escape route of the warriors) on a stand-alone ridge that separates two stream valleys. After only a half-mile (you have to be careful of drop-offs and slips, but the trail is not inherently dangerous), you double back a short distance on the ridge to a viewing spot that rivals any in Hawaii. The streams rush far below, and give way—on both sides—to steep cliffs that are often laced with waterfalls. Up the valley is a tree-filtered view of the Iao Tablelands and downstream is a blue-water view of Kahului Bay. From here, it's tempting the try the trail to Olowalu, but don't: The route is very overgrown and dangerous. See page 91 of Maui Trailblazer.