The world's most famous landmarks are plunged into darkness for one hour every year.
The global Earth Hour campaign raises awareness about the impacts of climate change. It started in Australia in 2007 and is now observed by participants in 187 countries, according to organisers.
Here are some major sites across the globe that dimmed their lights on Saturday 24 March 2018.
Sydney, Australia - Harbour Bridge and Opera House
Beijing, China - National Stadium (the "Bird's Nest")
Kuala Lumpur, Malaysia - Petronas Towers
Taipei, Taiwan - Taipei 101
Singapore - Supertrees at Gardens by the Bay
New Delhi, India - India Gate
Moscow, Russia - Christ the Saviour Cathedral
Minsk, Belarus - The Bolshoi Opera and Ballet Theater
Rome, Italy - Colosseum
Athens, Greece - Parthenon temple
Photos are copyright.