Lake Batur lies in the bowl of an ancient volcanic caldera in the highlands of north-central Bali, and from the rim above it the view is unforgettable. The lake is crescent-shaped, with a young black cone, Mount Batur, rising from the caldera floor at about 1,700 metres, still steaming from vents on its flank. The road runs along the crater rim at Penelokan, a name that means the place to look, and on a clear morning the mist lies in the basin like milk in a bowl.
This is one of the heartlands of Bali's remarkable irrigation system, the subak, which UNESCO has listed as a cultural landscape. For a thousand years the farmers of the island have shared water through a network of canals, tunnels and weirs, governed by priests and village councils who treat the water as a gift of the gods. At the centre of it stands the temple of Ulun Danu Batur, where offerings are made to the goddess of the lake, whose waters feed the springs that irrigate the rice terraces far below. The temple was moved up the slope after an eruption in 1926 buried the old village, and local people say the lava stopped at its gate.
The air is cool at this altitude, often damp, and a jacket is welcome. The road from Ubud climbs through Tampaksiring, and the bends tighten as you rise, with views over terraces and forest. Surfaces are generally good on the main road but poor on side lanes, and fog can come down quickly. On the far side of the lake, the village of Trunyan keeps an old practice of leaving its dead beneath a sacred tree, a custom that sets it apart from the rest of Bali.
Fuel is available in the larger villages around the rim, but it is sensible to start with a full tank. Sunrise treks up Mount Batur leave in the dark, and early mornings at the crater are crowded. Visit in the dry season, from May to September, and expect the air to be crisp and clear. Nothing quite prepares you for the sight of the lake in the first light.