Rurutu, located in the remote Austral Archipelago, is a magical land of migrating whales, abundant vegetation, limestone caves, and smiling faces. Accessed via Air Tahiti flights from Papeete five times per week, the car-free island is like no place else in French Polynesia. Comprised of a massive chunk of coral that was lifted up to form it, Rurutu has otherworldly topography – think sheer cliffs of pocked coral and giant caverns filled with ferns and stalactites. It is home to unique coral snorkeling, white-sand beaches, sacred marae, and fabulous biking (the island is very hilly).
A continuous reef rings Rurutu (so there's no lagoon), but despite the open ocean fronting it there are more beaches on Rurutu than most French Polynesia islands. The sand is also a bright white here and made from ground, bleached coral. Besides lounging on the beach, you can look for whales along the shores from roadside observation stations between July and October.
Note, unlike the rest of French Polynesia, the Australs get really chilly between May and November and are best avoided during this time. From December to April you'll find warmer temps, but it still isn't hot enough for air-conditioning most of the year.