Ranu Kumbolo is still part of the Bromo Tengger Semeru National Park area. Ranu or commonly called a freshwater lake at the foot of Mount Semeru has an area of about 15 hectares. Located at an altitude of 2,400 meters above sea level, Ranu Kumbolo is a source of clean water and a transit point for Semeru climbers. Ranu Kumbolo offers panoramic views of valleys and hills of pine forests with clear green lake water. In this lake there are many fish and grouse.
Ranu Kumbolo is the second post as well as a place to rest before traveling to the Jonggring Saloko crater on Mahameru Peak. A number of tired climbers can rest in this place by setting up tents on the edge of the lake while enjoying the calm lake water. There are also climbers who capture the moment by taking pictures at this location. At this post there is a simple inscription commemorating the death of a demonstrator, Soe Hok Gie, who died while climbing Mahameru on December 16, 1969. Don’t forget to prepare a thick jacket because the temperature can reach below 0 degrees Celsius. Ranu Kumbolo, the lake on the Mount Semeru hiking trail is like an oasis for climbers. The enchantment of the water which is dammed by a 15-hectare lake sometimes makes climbers unable to resist the urge to throw themselves in after being tired along a long track. However, the manager forbade the use of lake water for bathing because it is used as a source of clean water. One story says that in 1182 AD, King Kameswara from the Kingdom of Kediri found Ranu Kumbolo on his way to find a source of holy water. This is evidenced by the inscriptions on the edge of the ranu. The inscription is now protected by iron fences and covered in yellow and white cloth.
Apart from spiritual reasons, temperatures reaching single digits or close to zero degrees on an ordinary day can make the body cramp. If climbers are desperate to jump in, it is feared they will drown because the whole body is stiff in the icy cold water.