Tahiti is the largest island of the Windward group of the Society Islands in French Polynesia, an overseas collectivity of France. It is a tropical island located in the central part of the Pacific Ocean. Tahiti is composed of two roughly circular land masses joined by an isthmus: Tahiti Nui and Tahiti Iti. Both are the eroded remnants of now-extinct shield volcanoes. The terrain of Tahiti is mostly high and mountainous, with the beaches and coral reefs that surround the island supporting tourism and fishing industries.