Mount Batur, the small volcano inside a giant crater

The Mount Batur volcano is the summit most people mean when they say Batur, and it stands 1,717 m above sea level.^1,8 UNESCO calls that a modest height, then adds that the mountain is among the most beautiful in the region because of its double caldera, the crescent of its lake and the sunrise views that hikers enjoy.⁸ The number worth keeping in mind for a trek is that this is no alpine climb, yet it is high enough for the air on top to be very cold before the sun is up.⁹

The mountain sits at the center of two concentric calderas. The larger one measures 10 by 13 km and holds a lake on its southeast side; it formed when a magma chamber collapsed about 29,300 years ago, and the inner caldera collapsed about 20,150 years ago.³ What you climb is the cone that grew afterward inside the younger crater, an active stratovolcano about 700 m tall rising above Lake Batur.¹⁰ Seen from the rim, the layers are easy to read: a wall, a basin, a lake, and then the cone.

A geopark has been drawn around all of it. The Batur Geopark describes its area as two calderas with caldera walls, cones and craters, and UNESCO says the geopark spans 15 villages of the Kintamani district in Bangli Regency.^11,12 The same UNESCO text says the volcano is believed to have formed less than 30,000 years ago.¹³ So the thing you are looking at is young by geological standards, and still being shaped.

Lake Batur is an active caldera lake at 1,050 m with a surface of 16.05 km2 and an average depth of 50.8 m.⁴ Set the lake against the Mount Batur elevation and you get the scale of the cone above it. Its shoreline runs about 21.4 km; the volcano rises on its western side, while steep hills and Mount Abang, at 2,172 m, close in on the north, east and south.¹ UNESCO measures the crescent of the lake at 7 km long and 1.5 km wide.²¹

Indonesia.travel dates the lake to an eruption about 29,000 years ago and says you can rent a traditional boat to reach the middle or just sit by the dock.^22,23 The same page suggests tilapia from the lake's farms, Kintamani Ayam Betutu and Kintamani Arabica coffee, known for a citrus aroma, as lunch choices.²⁴ It is a quiet place after a very early morning.

Trunyan, on the east shore, is the village most visitors cross the water to see. The geopark puts it about 5 km from Kedisan, 32 km from Bangli city and 70 km from Denpasar, usually reached by boat, and the crossing from Kedisan takes about 30 minutes.^25,20 Its people lay the dead on the ground under a white cloth and a bamboo lid instead of cremating them, a tradition called mapasah.²⁶ It is a lived-in village, so ask before photographing anyone.