Time zone by time zone, nearly 4,000 cities and towns in 88 countries marked Earth Hour Saturday, by dimming nonessential lights from 8:30 to 9:30 p.m.

From an Antarctic research station, to the Great Pyramids of Egypt and several buildings in Washington, including the Smithsonian Castle, famous structures went dark in a campaign to highlight the threat of climate change.  

China participated for the fist time, cutting the lights at Beijing's Bird's Nest Stadium and the Water Cube.  

In the Chilean capital of Santiago lights were turned off at a number of buildings, including the Presidential Palace where President Michelle Bachelet hosted a dinner by candlelight for U.S. Vice President Joseph Biden.

Earth Hour organizers say there is no uniform way to measure how much energy was saved worldwide.

The event was first organized in Sydney in 2007.

Some information for this report was provided by AP.