Tonga is a country comprised of small islands in the South Pacific Ocean. The island of Tongatapu hosts the capital city, Nuku'alofa, and is one of the southernmost islands. The northernmost island, about 400 miles from Tongatapu, is Niuafo'ou. Two main island groups with many small islands are spaced evenly between the Tongatapu group and the Niua group: the Vava'u group and the Ha'apai group.