In this two-photo combination picture, the Eiffel Tower is shown with its usual lighting at left, and after the lighting was switched off at right, at the occasion of the Earth Hour, in Paris, France, on March 28, 2015. #

A before-and-after pair of images show the Niteroi Contemporary Art Museum (MAC) lit up and with lights off during Earth Hour in Niteroi, a neighboring city of Rio de Janeiro, Brazil, on March 28, 2015. [Click the image to view transition.] #

The Sydney Harbor Bridge and Opera House is shown before and after being plunged into darkness after fireworks started the Earth Hour environmental campaign, on March 28, 2015. [Click the image to view transition.] #

The Belarusian National Library is lit, then submerged into darkness for the Earth Hour environmental campaign in Minsk on March 28, 2015. [Click the image to view transition.] #

The Grand Palace is shown before and after its lights were turned off to mark Earth Hour in Bangkok on March 28, 2015. [Click the image to view transition.] #

The monument to Francysk Skaryna and the Belarusian National Library is seen before and after being submerged into darkness for the Earth Hour environmental campaign in Minsk on March 28, 2015. [Click the image to view transition.] #

Leifeng Pagoda is seen behind the West Lake before and during Earth Hour in Hangzhou, Zhejiang province, China, on March 28, 2015. [Click the image to view transition.] #

The Kremlin is seen before and after being submerged into darkness for the Earth Hour environmental campaign in central Moscow on March 28, 2015. [Click the image to view transition.] #

The Old Bridge is shown before and during Earth Hour in Mostar on March 28, 2015. The 16th-century bridge was destroyed during the war in Bosnia between 1992 and 1995, rebuilt, and opened again in 2004. [Click the image to view transition.] #

Pictures taken on March 28, 2015, in central London show the Houses of Parliament before and after being submerged into darkness for the Earth Hour environmental campaign. [Click the image to view transition.] #

The illuminated Serbian Parliament building is shown before, then in darkness when the lights are turned out for one hour to mark Earth Hour, in Belgrade, Serbia, on March 28, 2015. [Click the image to view transition.] #