Tonga is a Polynesian kingdom of more than 170 South Pacific islands, many uninhabited, most lined in white beaches and coral reefs and covered with tropical rainforest. The main island, Tongatapu, is protected by lagoons and limestone cliffs. It’s home to the rural capital of Nuku'alofa, as well as beach resorts, plantations and the Ha'amonga ʻa Maui, a monumental coral gate from the 1200s.