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, Total Rec takes a look at some of O'ahu's best novice, intermediate and advanced trails.

During the rainy winter months, 'Aiea Loop Trail is among the island's more vexing hikes, a simple 4.5-mile walk that morphs into a mud slog only Babe the pig or a monster truck could love. During the drier summer months, however, the Loop earns its reputation as one of O'ahu's most accessible and rewarding trails.

Moderate in distance and with only a few rolling hills, the trail is suitable for novice hikers and can be easily completed in two or three hours (or much less if trailrunning). Yet 'Aiea Loop is also popular with more experienced hikers who appreciate the diversity of plant life (albeit mostly introduced species), the numerous viewing points along the route, and the lack of conspicuous human management.

The trail starts just off the Keaiwa Heiau State Recreational Area upper parking lot in a dense grove of eucalyptus and Norfolk pines. Strawberry guava trees, which bear fruit in late summer, are also abundant. The narrow trail broadens after a short uphill section leading to an exposed vista with views of the city.

A stand of ironwood trees smothers surrounding plant life with its soft, hair-like needles but provides safe, cushiony footing as you wend along the initial contours of the mountain.

Following the ridgeline, you'll pass a pair of electricity towers before reaching a small clearing from which you can see the Wai'anae mountains.

The trail follows the ridge arcing right. Nearing the peak of Pu'u Uau, the path splinters left to 'Aiea Ridge and the Ko'olaus, but continue right along the main trail.

A tall 'ohi'a tree marks the farthest point of the trail. Halawa Valley is visible to the left as you begin your return leg, providing, according to your taste in scenery, a good or awful view of the H-3 Freeway.

The trail dips below a canopy of eucalyptus and koa and meanders gently downward. To the right, down a gully, lie the remains of a cargo plane that crashed in the early 1940s (not a Japanese bomber, as some claim).

Exiting a corridor of tall pines, you'll come to an exposed ridge and a decision: left toward Camp Smith or right to continue on to the end of the trail. Stay right.

The trail dips briefly into a gulch before rising abruptly along three long switchbacks. This portion of the trail requires careful footing to climb over rocks and roots and a bit of stamina to make it to the top, but it is not overly difficult for hikers of moderate fitness.

An electricity tower signals the end of the ascent. From there it's a short walk to the park's designated camping area.

The final portion of the hike is anticlimactic as you walk up the paved road back to the parking lot.

While the trail is wide, graded and consistently maintained, there are several fallen trees along the pathway that must be hopped. Most have been notched to allow for an easy step-over. The only physically challenging portion of the hike comes on the ascending switchbacks toward the end. However, this moderate challenge can be minimized by simply slowing your pace.

And while the final march back to the parking lot can be a grind, the lot does adjoin a nice grassy area that's perfect for sitting, rehydrating and reflecting on one of the island's easiest but most satisfying trails.

Reach Michael Tsai at mtsai@honoluluadvertiser.com.