If you are anywhere near the city of Tangerang in Cisoka district of Indonesia, it is recommended you pay a visit to the Blue Lake of Cigaru. It is a nice little tourist destination great for spending a quiet hour or two.
The bright, almost Prussian blue of the lake contrasts nicely with the white sands that surround it. The lake is however not a natural lake, but was formed as a result of sand mining.
Swimming in the lake is prohibited but if you are lucky, you may get to go for a boat ride. There is no regular boat service, but locals sometime offer their own boats for hire or will row you out themselves.