This 15-mile-long crown of serrated ridges and lush valleys is the most impressive of Kauai’s natural features—and also its most inaccessible. Only hardy, well-equipped hikers should attempt the full length of the 11-mile Kalalau Trail, which begins at Kee Beach and plunges up and down before ending at Kalalau Valley. The area’s last Hawaiian community lived in this 3-mile-wide, 3-mile-deep valley until the early 1900s. The valley, which can also be viewed from an overlook in Kokee State Park ★★★, is the setting for Jack London’s 1912 short story “Koolau the Leper,” based on a true tale of a man who hid from authorities determined to exile him to Molokai. (Today, marijuana growers and squatters bedevil rangers and others determined to protect the valley’s cultural treasures.) Most visitors just huff and puff 4 miles round-trip from Kee Beach to scenic but dangerously unswimmable Hanakapiai Beach, or make it a daylong adventure by adding a 4-mile, boulder-hopping slog to Hanakapiai Falls (see “Hiking”).

In late spring and summer, kayakers may explore the sea caves and oceanside waterfalls of Napali, but landing is only allowed at Kalalau and Milolii beaches; Kalalau requires a camping permit, while Milolii allows day use (see “Kayaking”). Nualolo Kai, the lower, seaside portion of another valley, has many archaeological sites, some under restoration, but only motorized raft (Zodiac) tours may land here (see “Boat & Raft [Zodiac] Tours”). The natural arch at Honopu Beach is a highlight of the snorkel cruises passing by, but may be examined closely only by the few capable of swimming here from Kalalau or a moored kayak—a dicey proposition much of the year.

The easiest, and most expensive, way to survey Napali’s stunning land- and seascape is by helicopter (see “Helicopter Tours”). However you experience it, you’ll understand why Napali remains the star of countless calendars, postcards, and screen savers.