It has rugged terrain, reaching up to Mount Gharat (797 m), the peak of the active stratovolcano at the center of the island. The most recent eruption was in 2013. The volcano has a 6 × 9 km caldera, within which lies a crater lake known as Lake Letas, the largest lake in Vanuatu. To the east of the lake is Siri Waterfall (120 m drop).