The Kingdom of Tonga is an archipelago of around 170 islands that spread across 700,000 sq km (270,000 sq mi) of ocean in the South Pacific Ocean. It is two thousand two hundred and fifty kilometers northeast of New Zealand and east of Fiji. The population of Tonga was estimated at 110,237 in 2004. The highest point in Tonga is an extinct volcano (1,046 m) on the island of Kao. The Kingdom is divided into the island groups of Ha’apai, Tongatapu and Vava’u. Nuku’alofa (Tongatapu) is the capital city and the main port. The islands are mainly raised coral limestone with some islands of volcanic origin. Tonga has a tropical maritime climate.