Information from Wikipedia Barossa Reservoir is a reservoir in South Australia, built between 1899 and 1902 to supply water to Gawler and other northern country areas. At the time of its completion, the reservoir was hailed as an engineering marvel, and at a total of 36 metres, was the highest in Australia. The thin arch of the dam retaining wall, curved against the pressure of the water, was an innovation considered radical, and attracted the Reservoir international attention. It was featured in the Scientific American and caused the American Engineers News to remark that its "boldness of design deserves to rank with the most famous dams in the world". Nowadays, the dam is notable for its parabola effect, where a voice can be heard clearly from one side to the other ? over 140 metres, end to end. This unusual acoustic phenomenon is a popular tourist attraction, and has earned the dam the title "Whispering Wall" Whilst visiting the "Whispering Wall" this was taken from the walk over to the other side of the arch wall - love the gum trees which surround the reservoir, have no idea what the contraption is presume it is something to monitor water quality and levels :)