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.

It's easy to get lost in Kahana Valley, in both the best and worst senses of the notion.

Two Danish hikers made headlines in 1999 when they veered off the path and wound up spending eight days along the summit ridge waiting to be rescued. Scores more have found their hike itineraries extended by hours, even overnight, after losing their bearings along the interlocking trails that meander through the valley.

Yet, for those with an aptitude for deciphering maps and understanding trail directions, the valley offers one of the most satisfying hiking experiences on O'ahu.

The 5-mile Nakoa Trail is suitable for beginners and can be extended into an 8-mile double loop trek for intermediate hikers. Both options offer a banquet of sensory experiences.

Let your eyes swim in oceans of green uluhe fern or fix your vision on the rough, Van Gogh-like strokes of fallen hala that shape the trail. Wince at the scrape of prickly scrub or sigh at the rush of cool stream water over your feet. Taste the valley's offerings of mountain apple, guava, mango and kukui nut. Listen to the trills of native songbirds above or to the clacking of bamboo trees in the distance. Or just stop and smell the ginger.

The trail can be accessed by entering the Kahana Valley State Park (maps are available at the park's visitor center) and proceeding — on foot, unless you are able to get the combination for the lock on the first gate — along the main road through a Native Hawaiian residential area.

Even in the middle of summer, the thick canopy of trees along the trail blocks much of the direct sunlight, allowing for a cool if sometimes humid hike.

After a brief descent toward Kahana Stream, hikers encounter a small dam at the first of nearly a dozen stream crossings along the double-loop trail. A rope extends the full width of the dam but footing along the moss-covered top of the structure is tenuous at best, especially when the stream is running fast. (Felt-bottom tabis are recommended for this and other larger crossings.)

The trail continues on the left and ascends away from the stream and toward the ridge line, initiating a series of gently rolling hills. At the first major junction, hikers should turn right and descend through a corridor of hala and hau plants.

The trail dips at another short stream crossing then rises along a broad, hau-covered terrace leading to a four-way junction. Here, hikers have the option of continuing straight ahead along the Nakoa Trail, turning right to return to the main road, or turning left to link with the second loop.

Those continuing with the longer, double-loop trail will follow the linking trail to a fork. To the right is the traditional start of the second loop; to the left is the end of the return portion.

Keeping right, hikers will pass a grove of mountain apple trees, which reach full fruit-bearing mode in the late summer.

After a pair of short but slippery stream crossings, hikers come to another junction (stay right) and then two more stream crossings.

The trail continues alongside and eventually across a larger side stream before reconnecting with Kahana Stream, which hikers will follow downstream until reaching a sharp left turn at a large pool.

Following the trail along the right bank heading downstream, hikers first cross the main stream, then a side stream, then the main stream twice more.

The trail forks once again a little farther downstream. The trail to the left leads to the return portion of the second loop, but hikers who still feel fresh will want to continue to the right, across a wide section of the stream and through a smaller side stream, to another large pool.

This is an ideal place to stop for lunch or a quick dip. Reflective hikers have wiled away many hours here, sitting on one of the large flat boulders and listening to the wind passing through the nearby bamboo grove.

The trail continues through the grove and up a narrow section of eroded trail that eventually leads back to the initial fork at the start of the second loop.

Taking the trail to the right, hikers return through the short linking path between the two loops and then to the four-way junction. To complete the trail, hikers should turn left to the uphill trail up to a terrace and follow the meandering trail along the side of the valley.

At a large water tank, turn right along the fence, connect with the paved road, and return to the first junction and the main road leading back to the visitor station.

The Kahana Valley double-loop trail isn't physically demanding, but it is considered an intermediate hike because of the number of navigational decisions hikers need to make to complete it without getting lost. For those who make the effort, the reward is an entrancing hike in one of the island's most lush and untouched valleys.