If you love a mystery, consider a vacation on Kauai, Hawaii.

Here's the mystery: what's it like on the neighboring Hawaiian island of Ni'ihau? This 550-square-mile island is the westernmost of the main Hawaiian islands and has been privately owned since 1864 by the Robinson family, which forbids tourists.

Ni'ihau (Nee-ee-how) is visible from the southwest shore of Kauai, lying low on the horizon 17 miles away. There are 200 or so native Hawaiians who live there and speak the Hawaiian language. In fact, it's the only place the language is spoken any more. It is taught in the island's only school, which goes K-8.

Islanders of course are free to leave and come back, so many of them do. They need to in order to get provisions from Kauai to live on the dry island, which is in the rain shadow of the ancient volcano cone on Kauai, Wai-ale-ale, "the wettest spot on earth" at 460 inches per year of rainfall. The Robinson family, which owns Ni'ihau, has maintained sheep ranches there.

A stunning form of folk art comes from Ni'ihau. These are Ni'ihau shell leis, tiny shells strung from many strands. These tiny luminous shells come in various colors, and so whole families collect them and sort them for size and color. Then the artist, usually a woman, sets to work, punching a hole in each shell using an awl often made from a bicycle spoke (there are no cars on the island). About half the shells shatter at this point. She chooses colors in such a way as to make a final product that is textured with color.

These tiny shells are still found on Ni'ihau, but not on neighboring Kauai where agricultural runoff has tended to kill off the shell-makers. The resulting shell leis are rare, hard to find, and precious. But if you look hard on Kauai, you can find them!

Hawaiian legend has it that the volcano goddess Pele had her original home on Ni'ihau. Then she traveled to Kauai, Oahu, and moved eastward until she found the Big Island of Hawaii, where she is today. Scientists say that the Hawaiian islands were formed as a plate of earth's crust moved slowly across an active lava vent. But Kauai was formed before Ni'ihau, which is sort of a side vent from the volcano that formed Kauai. As the crust moved slowly, Kauai was formed, then Oahu, and so on. Ni'ihau's current form is as an eroded lava dome on the eastern side of the island. Much of the rest is flat and sandy, with a couple of freshwater lakes.

It's possible to find a map of Ni'ihau, and pictures of its rock formations. But how can you go and see? In fact, the Robinson family is allowing a few forms of tourism now. Some helicopter tours from Kauai are allowed to land on remote beaches. And you can take a hunting safari, to control populations of feral bighorn sheep and Polynesian boars. In addition, scuba divers regularly dive off Ni'ihau.

All that is available from Kauai, Ni'ihau's big sister island 17 miles away. Kauai has immense charms of its own; not only does it have the usual beaches and surf, but it has incredible beauty on its northwest coast, called Na Pali, or The Cliffs.