Sarangan is a mountain resort on the eastern slopes of Lawu mountain. It's name means 'like a bird's nest', and it resembles a swallow's nest stuck to a cliff.
It has been popular since the Dutch created the lake, Telaga Pasir, by building a barrier across the outflow of water.
When I first came here in 1969 the place was desolate and dilapidated. But the surrounding nature was unspoilt, boating and swimming was great.
Nowadays accommodation extends to half the circumference of the lake, and most of the other half is occupied by food stalls. The water is dirty and they put up a sign 'swimming not allowed'.
Yet Sarangan is still the best base for climbing Lawu mountain, and for hiking among it's lower slopes.
If Sarangan is too developed for your taste, you may prefer
Telaga Ngebel on Wilis Mountain, some 50 km more to the east.