Sydneyis the most populous city in Australia, with a population of over 4.2 million people. Located on the south-eastern coast of Australia, it is also the state capital of New South Wales.
It set a fascinating example to the rest of the world in energy conservation, in the fight against global warming.
The city authorities simply switched off power supply to many areas for an hour.
Lights were out over the iconic coat-hanger bridge. The opera house was darkened. Families held candle-lit picnics on the edges of Sydney harbour, while thousands of suburban homes were blacked out.
It was called the Earth Hour and a chilling reminder to the residents of what is in store for them all if global warming continued unabated.
"Australians are ready to do something about climate change and it's time to start making a move," said Andy Ridley from the World Wildlife Fund Australia, one of the architects of the event.
"This country is the driest inhabited continent on the planet and we face some of the worst aspects of global warming," he warned.
Per capita this vast Australian continent is one of the world's largest producers of carbon dioxide and other gases that contribute to the warming of the earth's atmosphere.
A long-standing drought and serious water shortages in Australia have focused much attention in recent times on climate change.
Environmental worries have moved centre stage and they will be key issues in a federal election due later this year.
Sydney Morning Herald, a prominent newspaper, hailed the Earth Hour programme as a symbolic gesture that would raise the public awareness of the problem.
Bushfires, drought, more frequent cyclones and storms, drying rivers, melting glaciers, each piece of bad news strikes home like a new entry on a casualty list in a long war, the newspaper noted and called for concerted action to fight the looming danger.