The Ko'olau Range is stunning in more than one aspect, from its high, cloud-shrouded peaks to the steep fluted walls caused by centuries of erosion. At the back of the Nu'uanu Valley is another unique half-mile hike along the Ko'olau spine that takes climbers to a natural rock puka, or window, that frames the windward coast. During the 18th century, the final battle of King Kamehameha for unification of the Hawaiian islands took place near the Pali. His army invaded O'ahu, flanking the local army in the Nu'uanu Valley. It is said that the outnumbered O'ahu soldiers were cornered and driven off the cliffs to their deaths. Many years later, construction workers found hundreds of skulls below the Pali Lookout, perhaps from the fallen warriors. The stone notches cut out of the cliff above were for canons to defend the island.
The trailhead is located off of the Pali Lookout, behind the tour bus parking area. On any given day, the parking lot for the lookout is packed, and it has a parking fee of $3 for nonresidents. However, only a fraction of the lookout's visitors know about (or dare to take) the trail to the Puka. This hike is short, but strenuous and exposed to the elements. In fact, the steep valley walls form a powerful funnel for the trade winds, where even at the parking lot, gusts could easily knock over an unsuspecting person. That being said, if the wind is howling at the lookout, conditions on the way to the Puka are probably dangerous.
The hike starts through a dense bamboo forest, wasting no time as it quickly ascends the ridge. The first clearing in the trees brings a beautiful view of the windward side of the island and a glimpse into the trail ahead, heading up along the cliff. In these sections, a single misstep would be fatal. Use the ropes to navigate the steep, washed out sections. Around a half-mile in, hikers will come to a steep cliff, named the Shark's Fin, for its resemblance. The Puka is actually below you, on a worn rock ledge. Make your way down to the ledge for the best views through the window, but be careful, as the wind can be strong.
At this point, if you haven't been dissuaded by the difficulty of the trail so far and are feeling adventurous, a small trail leads to the left of the Shark's Fin, through the trees. After a short jaunt, this less-worn trail makes a sharp right turn, seemingly straight up the rocks with the aid of tattered ropes and tree roots. This section is easily a Class IV hike/climb and circumvents the Shark's Fin, reascending the ridge toward the summit of Lanihuli. Descend the same way you came, all the way back to the parking area, where flat ground will feel like a blessing.