Sydney
It is rare that Sydney has an opportunity to take the high moral ground.
Founded as a dumping ground for British felons, the harbour city has always had a shady reputation - historians say its first crime, a stabbing, was committed 24 hours after the First Fleet dropped anchor in Port Jackson.
No wonder, then, that Sydney's normally jaded citizens are cock-a-hoop about Earth Hour - an event which encourages householders, government agencies and private businesses to turn off their electricity for 60 minutes.
Launched in March last year as a Sydney-only initiative, Earth Hour was designed to show how ordinary citizens could make a small but important impact on global warming by reducing their energy consumption.
Such was the success of the inaugural event - an estimated 2 million Sydneysiders and 2,200 businesses turned off their power last year - that Earth Hour has now gone global: on Saturday, people in 24 cities around the world, including Toronto, Chicago, Copenhagen, Melbourne, Dublin and Tel Aviv, will flick the power switch.
The phenomenal growth of Earth Hour over the past 12 months has taken everyone by surprise, even the organising committee. This year, the number of people participating is expected to reach 25 million. 'We initially set a target of having 10 cities involved, if possible,' Earth Hour executive Andy Ridley says. 'So we were more than delighted when they kept on signing up.'