Lighting effects of the rainbow bridge on Chang'an Street in Beijing is switched off from 8 to 10p.m. on Saturday, June 21, 2008, the Summer Solstice. [Photo: Xinhua]

Colorful illuminations at main buildings in several Chinese big cities were switched off for hours on Saturday evening, the Summer Solstice, to save energy.

Xinhua News Agency reported that the actions were in concert with the "Earth Hour" activity that the World Wide Fund for Nature sponsored to boost energy-saving moves around the world.

Cities including Beijing, Shanghai, Zhengzhou and Hong Kong joined the Saturday's activity with blackout for at least one hour.

Initiated in 2007, the "Earth Hour" would be held worldwide on the last Saturday every March to aware people of the climate warming threat. Australia's Sydney was the first major metropolis to mark the activity.

Lighting effects of the rainbow bridge on Chang'an Street in Beijing is switched off from 8 to 10p.m. on Saturday, June 21, 2008, the Summer Solstice. [Photo: Xinhua]