Mount Tondano in the province of North Sulawesi, Sulawesi, Indonesia, has a 20 × 30 km wide caldera which was formed in the Late Miocene or Early Pliocene[2] by a massive eruption.

Lake Tondano lies in the east side of the caldera.

[1] The 5 km long and 3.5 km wide ellipsoidal Pangolombian caldera lies entirely within the Tondano Caldera, and formed from a large eruption of an older Somma volcano.

[2] In more recent times, the somma volcanoes of Soputan, Sempu, Lokon-Empung and Mahawu have been constructed along the rim of the Tondano caldera, with Soputan being the youngest and most frequently active of the group.

[2] Energy demand has been growing in Indonesia, and the Tondano caldera system could potentially provide clean energy for thousands of residents in northern Sulawesi.