In North America New York's Empire State Building switched off its lights, as did UN headquarters and Canada's Niagara Falls, whilst in South America Rio de Janeiro's iconic Christ the Redeemer statue went dark.
In Asia it was the Shanghai Tower, Seoul Tower, Kuala Lumpur's Twin Towers, the Burj Khalifa in Dubai, Taipei's 101 Building, some of Hong Kong's skyscrapers, Bangkok's Temple of Dawn and New Delhi's Indiate Gate that turned off the lights.
In Europe the Castle of Lisbon, the Arc de Triomphe in Paris, parts of St. Peter's Square in the Vatican, the London Eye and The Colosseum in Rome went dark too.
All of the cities marked it at 2030 local time.
Earth Hour is part of the Worldwide Fund For Nature's annual campaign to draw attention to the climate emergency.
The first Earth Hour was in Sydney, Australia in 2007.
Since then, over 190 countries and territories have taken part.
