From summit ridges to lush, green valleys, fast-running streams to bone-dry brush, Hawai'i's public access trails offer an unrivaled variety of unique hiking experiences — sometimes on a single trail. This summer, Advertiser reporter Michael Tsai takes a look at some of O'ahu's best novice, intermediate and advanced trails.

Experienced Hawai'i hikers know better than to pooh-pooh Pu'u Piei just because of its short overall distance.

The out-and-back trail extends just one mile from trailhead to summit, just two miles roundtrip. Yet, what the trail lacks in length, it more than makes up for in difficulty, with more than 1,700 feet of gain in that one not-that-short mile. Throw in highly unstable terrain; narrow, rock stretches of trail obscured by overgrowth; and a half-dozen red-herring offshoot trails, and you have a compact but very worthy challenge, indeed.

The trailhead is located just off Kamehameha Highway, near utility pole No. 313. It's a short hop into a ditch near a drainage tunnel, then a relatively easy walk up some plastic-lumber steps and a trio of moderate switchbacks leading to the side of the ridge.

Beyond the initial forest canopy, the trail opens at a juncture. While the right-facing path, which leads to a fish lookout, seems like a more direct route to the summit, keep left.

After crossing a rocky gully, you'll reach another junction. Take the broadest, most obvious path straight ahead and continue through the forest until you hit the edge of the ridge.

Again, the trail disappears for long stretches, lost either in loose, windswept dirt or beneath a thick carpet of ironwood needles. Even when visible, the trail forks at several small junctures, with each tempting side trail eventually overwhelmed by vines, brush and low-hanging branches.

In the first half of the hike, the gain in elevation comes in short stretches of loose, crumbly rock and slippery dirt slopes. During the second half of the ascent, the trail narrows and the angle of ascent increases significantly.

With unreliable handholds and grips on all sides, the unstable terrain can be challenging for even sure-footed, methodical hikers.

The trail levels at two, all-too-brief grassy areas flanked by uluhe fern and hala trees, then ascends sharply again along a rocky path.

The trail continues to narrow as you hike toward the towering figure of Pu'u Piei summit. The final sheer climb was once aided by cables fastened to the rock, but these appear to have been removed. Only expert hikers should attempt this climb without the cables, and only under optimal conditions.

Like its sister to the east, Pu'u Manamana, Pu'u Piei is a greater challenge than it appears on the surface. Despite the short distance, hikers should pack the same as they would for a longer hike — two liters of water, minimum — to account for the heat and humidity on the mostly exposed ridge and the likely level of exertion during the steep climb.

Hikers will also want to keep close tabs on their physical state as the steep descent on the return leg can be dangerous if one is fatigued.

Given the potential dangers, we can only cautiously recommend this otherwise lovely hike. If you attempt it, be sure you are in good physical shape, have packed all the essential hiking gear and are comfortable navigating a difficult-to-follow trail.