Bratan, Volcanic complex in northern Bali, Indonesia

Bratan, also called Catur or Tjatur, is a dormant caldera and stratovolcano at the northern side of Bali, Indonesia. The volcanic complex measures 11 by 6 kilometres and its highest point is the Batukau stratovolcano at 2,276 metres. Inside the caldera lie three lakes — Tamblingan, Buyan and Bratan — together with five post-caldera cones: Lesung, Tapak, Sengayang, Pohen and Adeng.

The complex formed during the Holocene through intense volcanic activity that shaped the landscape of northern Bali. The collapse that created the caldera left the depressions where the three crater lakes now sit.

Bratan takes its alternative names Catur and Tjatur from the same complex. The caldera's hot springs and fumaroles, heated by a magma chamber at depth, are used locally to generate electricity. The valley floor is covered in tropical forest and densely populated, so villages and farmland sit among the cones.

The area is reachable by paved roads from lower parts of Bali, and temperatures at this elevation are noticeably cooler than at the coast. Starting early in the morning gives the clearest views and the least foot traffic on the paths.

Lake Bratan, the main crater lake, feeds a large part of Bali's rice fields through an ancient irrigation system that is still in use today. This system, known as Subak, works without pumps or modern infrastructure and was recognized by UNESCO.