Lake Sarangan, Natural lake at Mount Lawu slopes, East Java, Indonesia.

Lake Sarangan is a natural lake on the southeastern slope of Mount Lawu in Plaosan, Magetan, about 16 km west of Magetan city. It covers roughly 30 hectares, reaches a depth of 28 metres and lies at 1,200 metres above sea level. The water comes from rain and surrounding springs; the far shore is a low bank of dark earth and rock below a hillside of scattered buildings and trees.

The lake occupies a natural basin on the southeastern slope of Mount Lawu, a dormant volcano; past eruptions are thought to have formed the depression later filled by rain and springs, and Jobolarangan Tuff deposits around the shore point to ancient pyroclastic activity. A road-widening project linking the lake to Grojogan Sewu waterfall in Tawangmangu, Karanganyar, was targeted for completion in 2007.

Sarangan hosts the labuh sesaji offering on the Friday Pon of the month Ruwah, Ledug Sura on 1 Muharram, and a fireworks party on New Year's Eve. Visitors circle the shore on horseback or by boat, and vendors sell satay kelinci, rabbit satay, around the water.

Lake Sarangan lies at about 1,200 metres on the south-eastern slope of Mount Lawu, roughly 16 kilometres west of Magetan; the Javanese source gives about 17 kilometres from Magetan and 15 from Tawangmangu. Air temperatures around the water range from 15 to 20 degrees Celsius. A road-widening project linking the lake with Grojogan Sewu waterfall in Tawangmangu was expected to finish in 2007.

The lake hosts four annual events: Labuh Sesaji on the Friday Pon of the month Ruwah, Ledug Sura on 1 Muharram, a fireworks party on New Year's Eve, and the mid-year school holiday. Around the water are 51 motorboats and 13 water becaks, three-wheeled pedal craft visitors can rent to circle the lake.