Polynesia Tonga Archipelago http://purl.obolibrary.org/obo/GAZ_00006917 An archipelago in the South Pacific Ocean, directly south of Western Samoa and about two-thirds of the way from Hawaii to New Zealand. Its 169 islands, 96 of them inhabited, are divided into three main groups--Vava'u, Ha'apai, and Tongatapu--and cover an 800 km-long north-south line. The largest island, Tongatapu, on which the capital city of Nuku'alofa is located, covers 257 km2. Geologically the Tongan islands are of two types: most have a limestone base formed from uplifted coral formations; others consist of limestone overlaying a volcanic base.