Nā Pali CoastSixteen miles of 4,000-foot sea cliffs on Kauaʻi's northwest shore, reachable only by foot, kayak, or helicopter

The Nā Pali Coast ("the cliffs" in Hawaiian) runs 16 miles along the northwest face of Kauaʻi, from Keʻe Beach in the east to Polihale State Park in the west. The cliffs rose as Kauaʻi tilted northwest five million years ago — the oldest of the main Hawaiian islands — and erosion has since carved them into the fluted green amphitheaters that show up on every postcard. The state park was created in 1983 specifically to keep the coast roadless; the 2009 expansion added the Hono O Nā Pali Natural Area Reserve to the east.

Three ways in, no fourth. By foot: the Kalalau Trail starts at Keʻe Beach and runs 11 miles to Kalalau Beach, gaining and losing 5,000 feet over five major valleys; the first two miles to Hanakāpīʻai Beach are accessible without a backcountry permit, the rest requires advance booking through camping.ehawaii.gov. By sea: catamaran tours run out of Port Allen and Hanalei from April through October, four to five hours with snorkel stops at the Open Ceiling Cave; sea kayaks launch at Polihale and finish at Keʻe (15 miles, 7–9 hours, advanced paddlers only). By air: doors-off helicopter tours from Līhuʻe run year-round at $300–$400 a seat, 50–65 minutes for the full Kauaʻi circle including Waimea Canyon.

Plan around weather. Winter swells (November–March) shut down most boat launches and make the Kalalau Trail's stream crossings dangerous; April through October is the short safe window for sea travel. The cliffs catch every cloud — Mount Wai'ale'ale, the catchment behind them, averages 450 inches of rain a year — so trails turn to ankle-deep mud after a single afternoon shower. Bring real waterproof footwear, more water than you think you'll need, and never turn your back to the ocean at Hanakāpīʻai (the beach has the highest drowning rate per visitor of any Hawaii beach).