The island is located at the southern end of the
New Georgia Islands archipelago. To the north-west is the island of
New Georgia and to the south-east is the island of
Nggatokae. The largest saltwater
lagoon in the world, the
Marovo Lagoon, encircles most of the island. Vangunu is a volcanic island, dominated by an inactive
Pleistocene stratovolcano with a height of , whose
caldera slopes are now covered with thick jungle forest. Around to the south of Vangunu lies the
submarine volcano known as
Kavachi, the only currently active volcano of the archipelago, and one of the most active submarine volcanoes in the south-west
Pacific Ocean. ==Ecology, flora and fauna==