The Blue Lake, Mount Gambier’s jewel in the crown, still puzzles scientists today. A gorgeous spot, 75m deep, that turns to an incredible shade of blue in the summer months...and no one is entirely sure why! Walking the 3.6km trail around the rim is a fantastic experience, and provides ample opportunities for stunning photos. Or take an Aquifer Tour, in a glass-panelled lift down an 80m tunnel. The lake is open 24 hours a day, all week.