This longest river in Java flows along the eastern edge of the town from its source in the lime stones hill of the south, near East Java border to its mouth nearby Surabaya, on the Java sea. Regretfully, the river is now shallow it is not navigable anymore. But in the past it was an important link between Solo and the north cost of East Java.
It length is 600 km flowing in 2 provinces which are Central Java Province and East Java Province with the irrigation width 16.000 km2, was the biggest and the main river basin area. It rises on the slope of Mount Lawu volcano (10,712 feet [3,265 m]) and the southern limestone range (Sewu Mountains) and flows north, then east to discharge into the Java Sea at a point opposite Madura Island, northwest of Surabaya. In recent 30 years development of irrigation facility at the Bengawan Solo river area have reach a significant level of development. This was mark by the completed of irrigation building, which still in progress or even have been built such as reservoir, dam, dike, irrigation net, and others. Investment have been spent to reach this development level is very big. Those buildings have functions as a flood controller, Hydraulic Power Generator, water supply for farming, industry, drink water, fishery, and others.
There is a well-known song 'Bengawan Solo' composed by Mr. Gesang. In the central Javanese city of Solo, a statue of Gesang Martohartono looks over the gently flowing Bengawan Solo, or Solo River. It was the famous Indonesian singer-songwriter Gesang, who composed the celebrated Indonesian melody "Bengawan Solo" during World War II -- when the country was under Japanese occupation. The song describes the legendary river in a poetic and nostalgic way, that it is surrounded by mountains, its sources are near the city of Surakarta, that it ends in the sea, and that the merchant class always makes use of it. It is in the local Keroncong style, a popular folk style with influences from Portuguese. The Japanese, who occupied the country during World War II, brought the song with them to Japan after returning from the war. There, and also in the rest of Asia and later worldwide, the song became very famous.