Chowilla Dam
The 928th tallest dam in the world
Chowilla Dam was a proposed water storage reservoir on the Murray River in the 1960s. The dam wall would have been in South Australia, but the reservoir behind it would have stretched upstream into Victoria and New South Wales. The site was selected in 1960. Early preparations for its construction were conducted before the project was halted. These included a 23 km service railway from the Barmera railway line, which was dismantled without ever being used.
Dam data from Wikidata (CC0) plus curated additions. Summary from Wikipedia (CC BY-SA).