The Mount Gambier Volcanic Complex state heritage area recognises it as Australia's most recent site of volcanic activity and a major tourist destination since the 1880s.
The Mount Gambier Volcanic Complex consists of a series of craters and other volcanic features on the southern edge of the city of Mount Gambier, around 480km south east of Adelaide.
The state heritage area includes the sides and rim of the craters that form the Blue Lake, Leg of Mutton Lake, Valley Lake and Browne Lake. The volcanic feature known as the Devil's Punchbowl is also included in the area.
This volcanic complex was created around 4,000 years ago. The area's shallow water table was heated by the volcanic activity, causing steam pressure to build during eruptions. This created the characteristic craters (maars) and steam vents in the area.
The explosions exposed the water table, filling the craters to create the four lakes that have become well-known tourist attractions.
The largest crater is the Blue Lake, named for the cobalt-blue colour of its water between November and March. The Lake provides Mount Gambier's water, and it is recognised as one of the best-preserved examples of this type of crater in the world.
This crater-lake complex is an important geological site for teaching and researching volcanic activity in Australia. Mount Gambier is also a South Australian Geological Monument.