Countless landmarks captured in photos around the world went dark on Saturday, March 31, 2012 as a part of the Earth Hour celebration to raise awareness in a global effort for climate change.

Each year, Earth Hour is held on the last Saturday in the month of March where for one hour, lights are switched off. Last year, 135 countries participated and grew to 147 this year, according to the World Wildlife Fund (WWF).

Earth Hour 2012 is a celebration of people power; the world's largest mass event in support of the planet, WWF official Dermot O'Gorman said in a statement.

Earth Hour began online in Sydney, Australia with the dimming of the Harbour Bridge and Opera Hose and since has spread around the world to the Tokyo Tower to the Sky Tower in Auckland in New Zealand. In Paris, France, over 230 monuments and landmarks went dark on Saturday including the Notre Dame Cathedral and the Arc de Triomphe. The Eiffel Tower, however, only went dark for five minutes due to security measures, according to the Mayor's office. In New York, the Empire State Building went dim as well as the National Cathedral in Washington.

View the slideshow to see photos of Earth Hour 2012.

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A combination picture shows the Palace of Culture during top and after Earth Hour in Warsaw March 31, 2012.
A combination picture shows the Palace of Culture during (top) and after Earth Hour in Warsaw March 31, 2012. Reuters
A combination photo shows financial district during Earth Hour bottom in Shanghai March 31, 2012.
A combination photo shows financial district during Earth Hour (bottom) in Shanghai March 31, 2012. Reuters
A combination photo of Marina Bay Sands hotel and ArtScience Museum R, before top and during Earth Hour in Singapore March 31, 2012.
A combination photo of Marina Bay Sands hotel and ArtScience Museum (R), before (top) and during Earth Hour in Singapore March 31, 2012. Reuters
A combination shows the 97-metre monument Baiterek before L and during Earth Hour in Kazakhstans capital Astana, March 31, 2012.
A combination shows the 97-metre monument Baiterek before (L) and during Earth Hour in Kazakhstan's capital Astana, March 31, 2012. Reuters
A combination photo shows the quotHam Ca Mapquot building before top and during Earth Hour in Hanoi March 31, 2012.
A combination photo shows the "Ham Ca Map" building before (top) and during Earth Hour in Hanoi March 31, 2012. Reuters
A combination photo shows a Soviet era skyscraper on Kotelnicheskaya Embankment near the Moskva River before top, and during Earth Hour in Moscow March 31, 2012.
A combination photo shows a Soviet era skyscraper on Kotelnicheskaya Embankment near the Moskva River before (top), and during Earth Hour in Moscow March 31, 2012. Reuters
A combination photo shows the Serbian Parliament building, before top and during Earth Hour in Belgrade March 31, 2012.
A combination photo shows the Serbian Parliament building, before (top) and during Earth Hour in Belgrade March 31, 2012. Reuters
A combination picture shows the hill of the Acropolis before top and during Earth Hour in Athens March 31, 2012. E
A combination picture shows the hill of the Acropolis before (top) and during Earth Hour in Athens March 31, 2012. Reuters
A combination photo shows the Hermitage museum during top and after Earth Hour in St. Petersburg March 31, 2012.
A combination photo shows the Hermitage museum during (top) and after Earth Hour in St. Petersburg March 31, 2012. Reuters
A combination picture shows power lines crossing in front of the Sydney Harbour Bridge and city skyline on March 29, 2012 top before Earth Hour, and during Earth Hour March 31, 2012.
A combination picture shows power lines crossing in front of the Sydney Harbour Bridge and city skyline on March 29, 2012 (top) before Earth Hour, and during Earth Hour March 31, 2012. Reuters
A combination photo shows the Mikhaylo St. Michael Golden Cupolas Cathedral before top and during Earth Hour in Kiev March 31, 2012.
A combination photo shows the Mikhaylo (St. Michael) Golden Cupolas Cathedral before (top) and during Earth Hour in Kiev March 31, 2012. Reuters
A combination photo shows the Empire State Building with the lights turned off L, and with the lights switched back on in participation with Earth Hour, in New York, March 31, 2012.
A combination photo shows the Empire State Building with the lights turned off (L), and with the lights switched back on in participation with Earth Hour, in New York, March 31, 2012. Reuters
People light candles during Earth Hour after lights were turned off in Cali March 31, 2012. Lights started going off around the world on Saturday in a show of support for renewable energy.
People light candles during Earth Hour after lights were turned off in Cali March 31, 2012. Lights started going off around the world on Saturday in a show of support for renewable energy. Reuters
A combination photo shows The Angel of Independence statue with the lights turned off top and with the lights switched back on in participation with Earth Hour in Mexico City March 31, 2012.
A combination photo shows The Angel of Independence statue with the lights turned off (top) and with the lights switched back on in participation with Earth Hour in Mexico City March 31, 2012. Reuters
A combination photo shows The City Hall of Puebla with the lights turned off top and with the lights turned back on in participation with Earth Hour in Puebla March 31, 2012.
A combination photo shows The City Hall of Puebla with the lights turned off (top) and with the lights turned back on in participation with Earth Hour in Puebla March 31, 2012. Reuters
A combination photo shows The Palacio de los Capitanes with the lights turned off top and with the lights turned on during Earth Hour in the Central Place of Antigua, about 42 km 26 miles from Guatemala City, March 31, 2012.
A combination photo shows The Palacio de los Capitanes with the lights turned off (top) and with the lights turned on during Earth Hour in the Central Place of Antigua, about 42 km (26 miles) from Guatemala City, March 31, 2012. Reuters
A combination picture shows national library before top and after the lights are turned off during Earth Hour in Minsk, March 31, 2012.
A combination picture shows national library before (top) and after the lights are turned off during 'Earth Hour' in Minsk, March 31, 2012. Reuters
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