A wave of darkness travelled the world on March 26 2011 as countries observed a symbolic Earth Hour by turning off lights, the Voice of America reported.
 
People in 134 countries pledged to participate in the event at 8.30pm in each time zone. The campaign aims to inspire people to help the environment by changing their behaviour to conserve resources.
 
Well-known landmarks like the Sydney Opera House, Paris' Eiffel Tower, and New York City's Empire State Building all pledged to go dark for the hour.
 
Others taking part included Brazil's Christ the Redeemer statue, Malaysia's Petronas Towers and Beijing's "Bird's Nest" stadium, which hosted the 2008 Olympic Games.
 
The World Wildlife Fund organises the annual Earth Hour event.
 
The director of the conservation organisation, Jim Leape, said the increasing reach of the movement is a sign people and governments are recognising that everyone can play a part in "building a sustainable future."
 
Leape said participation has especially grown among emerging economies, like India. He said this was good news, as those countries are playing larger roles in global affairs.
 
The first Earth Hour was observed in Sydney, Australia, in 2007.
 
The United Nations turned out the lights at its New York Headquarters, the UN News Centre said.
"Let us join together to celebrate this shared quest to protect the planet and ensure human well-being. Let us use 60 minutes of darkness to help the world see the light," UN Secretary-General Ban Ki-moon, who has called climate change "one of the defining issues of our era," said in a message.
The BBC said that in Scotland, Edinburgh Castle, the Scottish parliament building and the Falkirk Wheel, usually lit up at night, were among the landmarks marking Earth Hour.
With the official support of more than 350 cities across Austria, Hungary, the Czech Republic, Romania, Bulgaria, Serbia, Croatia and Ukraine, Earth Hour was observed by thousands of people in Central and Eastern Europe, the WWF said.

In Austria, president Heinz Fischer was among the official supporters of Earth Hour.
 
According to a statement issued by his office, "The Federal President of Austria welcomes all activities such as Earth Hour to make known the drastic impacts of climate change to all Austrians and people who live in Austria".

The capital Vienna officially took part in Earth Hour for the first time.
 
At 8.30pm the city saw the lights go off on the famous Vienna City Hall building.
 
Lights also went off on the historic Schönbrunn Palace on the outskirts of Vienna.  
 
Outside of Vienna, 11 further cities supported the event. Among these were the historic towns of Innsbruck, Linz, Klagenfurt and Salzburg. In Salzburg, lights went out on 20 landmarks, among them Castle Hohensalzburg and the Statue of Mozart.

Sixty-six cities took part in this year’s Earth Hour in Hungary.
 
In the capital Budapest, more than 5000 people congregated in the Castle area of the city and heard celebrities talk about climate change, environment protection and why they support Earth Hour.
 
The Castle area is the highest point in Budapest and at 8.30pm Earth Hour supporters could see lights being turned off throughout the city.

Budapest Airport closed an entire runway as a commitment to Earth Hour.
 
The runway illuminators have a total capacity of 84000 Watt and their light can be seen from 20 kilometres above. Unnecessary lights in the airport buildings were also switched off. Passenger safety was at no time under risk.

In the Czech Republic, Earth Hour took place for the second time. This year four times more cities and towns – a total of 120 - joined Earth Hour. Among these cities were four regional capitals.

In the second biggest city, Brno, citizens were invited to join a special event.
 
The "Enjoy the darkness" event was an evening of culture with movies about darkness, lectures on climate and light pollution and several concerts taking place in the dark. A guided city walk took Earth Hour supporters to some of the "dark" corners of the city, stopping at art shops, cafés and restaurants that were operating only by candle light.

In Romania, lights were turned out on the Parliament Palace in Bucharest, one of the biggest buildings in the world and certainly the largest parliamentary building. It consumes in one hour what a household consumes in a year.

Fifty-two Romanian cities, including Bucharest, celebrated Earth Hour this year.
 
In the capital Bucharest, with the support of the municipality and nine biking associations, WWF organised a bike march which gathered about 500 people, who crossed the main city boulevards.
 
In front of the Romanian Athaeneum which went dark at 8.30pm, an audience of supporters enjoyed an unplugged concert hosted by popular musician Zoli Toth`s band SISTEM and by Romanian choir SOUND.

"Every day we consume a lot of energy that we don’t actually need. If we are a bit more careful and care about future generations, we can decrease our carbon footprint significantly in the future. Everything depends on us", veteran Earth Hour ambassador Zoli Toth said.

In Bulgaria, a series of free concerts took place in several of Sofia’s top music clubs.
 
Supporters of Earth Hour enjoyed the music of popular Bulgarian rock and ethno bands at simultaneous acoustic concerts, dedicated to Earth Hour, the WWF statement said.
 
Major buildings in central Sofia remained in darkness for one hour, among them the buildings of the National Assembly, cabinet ministries, Bulgarian National Bank, Sofia University Saint Kliment Ochridski, Alexander Nevsky Cathedral, Ivan Vazov National Theatre, and historical monuments, Bulgarian National Radio said.
 
Outside of the capital Sofia, 46 further cities showed their support, the WWF said. Lights went out on administrative buildings, historic monuments and public spaces all over the country.

This was the third Earth Hour for Bulgaria and this year the event was held under the patronage of EU Commissioner Kristalina Georgieva.
 
Top Bulgarian tennis players Wimbledon semi-finalist Tsvetana Pironkova and Junior Wimbledon and US Open winner Grigor Dimitrov were ambassadors of the event.

"I believe that Earth Hour shouldn’t be just turning off your lights for an hour once a year. We should all think how we can contribute to saving our planet every day. The Earth is not our home only, it will need to be the home of our children too," Pironkova said.

"Really, it’s not difficult and I believe that everyone can work on their environmental footprint and be more responsible towards the environment," Dimitrov said.

In Serbia, 40 cities and municipalities participated in Earth Hour, the biggest events taking place in Belgrade and Nis.
 
By 8.30pm, supporters of Earth Hour had gathered on the Republic Square in central Belgrade. They could leave environmental messages pledging their understanding and support for the need to "go beyond the hour".

Organised for the third time in Croatia, Earth Hour got the support of Croatian president Ivo Josipovic.
 
Fifteen cities signed up for the event and the lights went out for the first time on Unesco heritage sites Dubrovnik City Walls and Diokletian Palace in Split.

In Ukraine, capital Kyiv led 32 further cities in observing Earth Hour.
 
Lights went out on the busy Kreschatik boulevard and the historic orthodox Christian Kievo-Pecherskaya monastery. Earth Hour supporters enjoyed an hour of acoustic music with popular Ukrainian singer Dmitriy Shurov and music band "Bahroma" at the Contemporary Art Centre M17.

In Odessa, the historic centre of the city, including the Opera and seaside boulevard, were also shrouded in darkness. At 8.30pm people could join a street concert near the city hall. At the end of the concert people could write their pledges to the Planet on lanterns and let them fly into the night sky.

"If each one of us begins to monitor the quantity of gas, water and electricity used, the numbers for a huge country like Ukraine will be enormous. In reality it is so simple to change our behaviour", said Earth Hour veteran and popular clothes designer Lilia Poustovit, who has been an ambassador to the Ukrainian campaign since 2009.