<Tr> <Th> Surface area </Th> <Td> 0.62 km (0.24 sq mi) </Td> </Tr> <Tr> <Td_colspan="2"> Website http://www.sawater.com.au/community-and-environment/our-water-and-sewerage-systems/water-sources/reservoir-data/barossa-reservoir </Td> </Tr> <P> Barossa Reservoir is a reservoir in the Australian state of South Australia, built between 1899 and 1902 to supply water to Gawler and other northern country areas . Built at a cost of almost £ 170,000 the reservoir was hailed on completion 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" (see Whispering gallery). </P> <P> During construction large stones were used in the wall to save concrete and tram rails were used to reinforce the upper section . The Barossa Reservoir was formed by damming the Yettie Creek gorge in the northern Mount Lofty Ranges, a feat that took over 400 men . Its water comes through a two - kilometre tunnel, carved by horse power, from the South Para River and Reservoir, and is supplemented by the Warren Reservoir and the River Murray . In addition to Gawler and country, a filtration plant constructed in 1982 allows the Reservoir to supply the suburbs of Munno Para and Elizabeth . </P>

Where is the whispering wall in south australia