The Siwi area in the interior of Tanna has a series of hot springs and geothermal features fed by the same volcanic system that powers Mount Yasur. The springs are not developed for tourism and the pools are not suitable for bathing (the water is too hot in places), but the landscape — steaming vents, mineral-stained ground, and the smell of sulphur — is striking.
The area is worth visiting as part of a broader exploration of Tanna's volcanic landscape. A guide is useful here, both for navigation on unpaved tracks and for context about the geology and the local communities' relationship with the land.