A volcanic crater lake that turns a vivid cobalt blue each summer, ringed by a 3.6km walking and cycling track.
A lake that changes colour
The Blue Lake fills one of the craters of the Mount Gambier maar volcanic complex, the last to erupt some 28,000 years ago. From around November to March each year the water transforms from steely winter grey to an intense, almost luminous cobalt blue - a phenomenon linked to the way calcium carbonate crystallises and scatters light as the water warms.
The lake is also Mount Gambier's drinking-water supply, sitting up to 70 metres deep. A sealed 3.6km path circles the rim, with several lookouts, and the historic Aquifer Tour descends through the 1880s pump station to a viewing platform at the water's edge.
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Last verified 8 August 2026 · source: Visit Mount Gambier (official tourism site)
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Blue Lake - frequently asked questions
Why is the Blue Lake blue?
From around November to March the Blue Lake changes from grey to a vivid cobalt blue. Scientists link this to warming surface water causing dissolved calcium carbonate to crystallise into fine particles that scatter blue light. By autumn the water cools and the colour fades back to grey.
Can you swim in the Blue Lake?
No. The Blue Lake is Mount Gambier's drinking water supply, so swimming, boating and other water contact are not permitted. You can walk or cycle the 3.6km sealed track around the rim and view the lake from several lookouts.
How deep is the Blue Lake?
The Blue Lake fills a volcanic crater and is around 70 to 75 metres deep. It sits within the Mount Gambier maar volcanic complex, the most recently active volcano on the Australian mainland.
Can you tour the Blue Lake?
Yes. The Aquifer Tour descends through the historic 1880s pump station via a glass-panelled lift to a viewing platform at the water's edge. The sealed rim path is open year-round and free to walk.
Sources
- Visit Mount Gambier (official tourism site) (accessed August 2026)
Image credits
- WV banner Limestone Coast Mt Gambier Blue Lake.jpg by Admella1859 , CC0 via Wikimedia Commons