NEW YORK: The UN headquarters in New York, the pyramids of Egypt and Rio's Christ the Redeemer statue were among top world monuments plunged into darkness for an hour Saturday to put the spotlight on climate change and its impact on the planet.

Organized by environmental watchdog WWF, the 13th edition of Earth Hour saw millions of people across 180 countries turning off their lights at 8:30 p.m. to highlight energy use and the need for conservation.