The Blue Lake at Mount Gambier in the South-East of South Australia is a unique attraction.
It has formed in the vent of a recent volcano, on the side of which the City of Mount Gambier has been built. The city relies on the lake as its source of potable water. Water in the lake is exceptionally clear, the quality is very good, but it is hard due to infiltration through limestone which underlies the district.
This hardness can be easily removed by household water softeners.