The City of Lights also turned off the Eiffel Tower's nightly twinkle to mark Earth Hour. Paris Mayor Anne Hidalgo dimmed the lights Saturday on the city's most famous monument for an hour.

In Italy, public buildings and historical monuments in 400 cities participated in Earth Hour. Lights were also switched off at St. Peter's Basilica at the Vatican.

Some of most emblematic architectural treasures in Spain participated, including the Alhambra palace in Granada and Barcelona's La Sagrada Familia basilica.