An arid, somewhat barren island sits 18 miles to the west of Kauai. Pronounced NEE-ee-how, this privately owned outpost is still home to about 250 locals who primarily speak Hawaiian. Residents eschew technology and cleave to old traditions, from hunting with ropes and knives to fishing with spears and nets. Niihau Helicopters offers half-day excursions ($440 per person) to this mysterious "Forbidden Island": Guests land on secluded beaches that are studded with shells and balls of glass that wash up on the shore, and often find themselves basking on the sugar-white sand alongside endangered Hawaiian monk seals. The Holo Holo catamaran also makes the crossing after sightseeing along the Nāpali Coast, for roughly half the price.