Lake Eyre ( \ / ˈɛər \ / AIR ) , officially known as Kati Thanda-Lake Eyre , is the lowest point in Australia , at approximately 15 m ( 49 ft ) below sea level ( AHD ) , and , on the rare occasions that it fills , the largest lake in Australia and 18th largest in the world .
Lake Eyre ( pronounced `` air '' ) is the lowest point in Australia , at about 15 m ( 49 ft ) below sea level .