Some 20 kilometres west of the Victorian Border in the state of South Australia is picturesque Mt. Gambier. The city snuggles beside the base of an extinct volcano and is situated above an eloborate network of subterranean lakes.

Some 23,000 people have made Mt. Gambier their home city.

The extinct volcano called "The Blue Lake" is said to be over 200 metres deep and changes colour from grey to a brilliant cobolt blue from November and remains that way until March. This changing of the colour is an unexplained phenomenon.

The Blue Lake is the source of the town's water and is replenished by the subterranean lake system which stretches from the southern coast to Broken Hill in northern New South Wales, a distance of some 700 kilometers to the North.

Picture © Dean Niclasen

These subterranean waters are linked to the surface by a series of shafts, craters, small lakes and deep caves. Over 150 of them in the Mt Gambier region alone. Some of these sinkholes and caves are world famous such as Piccannine Ponds, The Shaft, Kilsby's and Ewens Ponds. The picture is of Piccannine Ponds looking up from the plaque through the slot to the surface.

Little Blue Lake is another sinkhole located not far from the Blue Lake and is used by the locals as their swimming hole. Quite often the locals jump into the water from the surrounding cliff faces. Under the water another world has developed. Over the years numerous pieces of junk have been dumped into this hole, cars, table and chairs, a safe, street signs, a petrol pump and numerous tyres. These items have been assembled into a scene from the past. The car is next to the petrol pump which has table and chairs nearby etc.

Piccannine Ponds is another sinkhole in the Gambier region and has exceptionally clear water. At 36.5 metres there is a plaque warning divers not to dive beyond this point. Entry into the pond is by a platform as pictured below. Swimming over the reed curtain the water becomes even clearer and you find yourself reading the plaque some 36.5m below. At the other end of the slot is the entrance into the cave known as the cathedral. Within the cathedral the bottom drops away some 40m to what is known as the bathtub. At the bottom of the bathtub there is a small tunnel that continues even further. Piccannine Ponds is an exciting and enjoyable dive anytime. To dive at this location a permit must be gained and an hour time slot allocated. There is a maximum of 4 divers and 2 snorkelers at any one time.