The 11 x 6 km wide Bratan caldera in north-central Bali is actually a complex of peaks and contains three caldera lakes. Several post-caldera stratovolcanoes straddle its southern rim; the largest post-caldera cone, Batukaru, is 10 km to the SW. The cones are well-formed, but covered with thick soils and vegetation; they are thought to have been inactive for hundreds or thousands of years.

Tapak and Lesong cones are not covered by deposits of the youngest dacitic pumice eruptions of nearby Batur volcano, and are thus <23,000 years old. The Buyan-Bratan geothermal field within the caldera has been developed to produce electrical power, and hot springs are located in more than a dozen locations.