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PHOTOS: Landmarks Around the World Go Dark to Promote Environmental Awareness

In just a single hour every year, millions of people worldwide turn off their lights, and in darkness they unite to promote environmental awareness.

Earth Hour, which is organized by the conservation organization World Wildlife Fund (WWF), was held for the ninth year for one hour on March 29.

With this year's participation outdoing any other year, many were able to capture images of some of the 1,400 landmarks and close to 40 UNESCO World Heritages Sites that were dark and silenced for one of the few hours all year.

In 2014, over 7,000 cities and 162 countries and territories participated in Earth Hour. But, this year 172 countries and territories switched off their lights to participate in what has become the world's largest grassroots movement for the environment, according to Earth Hour's website.

"From the Earth's extremes to outer space, people came together to send a clear message that action on climate is on top of their agenda," said Sudhanshu Sarronwala, the Earth Hour Global chair of the board of directors, in a press release.

Social media has also helped bring awareness to the movement with over 384 million social media posts and tweets about Earth Hour between March 23 and March 29, according to its website.

"Earth Hour confirms our belief that in order to change climate change we need to act together," Sarronwala said.

In 2014, electricity used for lighting made up about 11 percent of the total U.S. electricity consumption, according to the U.S. Energy Information Administration.

The amount of electricity used on lighting in residential homes appears to have stayed relatively steady based on EIA data from 2012 and 2014. In both these years, about 14 percent of electricity used in residential homes was for lighting.

While one of the main features of Earth Hour is turning off the lights, some cities held festivals and advocated environmental policy reform.

Check out these images of the landmarks that speak loudly toward the impact WWF hopes to continue to make for future Earth Hours.

The next hour that WWF and its supporters stand together in darkness is scheduled for March 19 of next year.

The Eiffel Tower - Paris, France

The Earth Hour City Challenge jury choose Seoul as the Global Earth Hour Capital. But, Paris was on the list of the 16 national winners that were considered by the jury for the Global Earth Hour Capital.

The Indian Presidential Palace - New Delhi, India

While New Delhi was not a national winner, Thane, India, was a national winner. According to the Earth Hour website, the 163 cities that participated in the Earth Hour City Challenged were evaluated based on their ambition and innovation for low carbon development.

The Kremlin - Moscow, Russia

As Kremlin switches off its lights, citizens also gathered to collect 70,000 signatures to preition for a moratorium on the exploration of Arctic oil, which according to WWF could have significant environmental and climate impacts.

The Serbian Parliament Building - Belgrade, Serbia

The Taipei 101 skyscraper - Taipei, Taiwan

The Sydney Harbour Bridge - Sydney, Australia

Sarronwala said in a press release that "Earth Hour turns out the lights, but the future of our planet is brightened by the countless individual actions of supporters around the world." According to this same press release, Australia hosted a sustainable candle-lit dinner to emphasize climate change's impact on agriculture.

Skyline - Dallas, Texas

The India Gate -New Delhi, India