More than a dozen Swiss cities participated in the global Earth Hour climate campaign on Saturday by turning out the lights for one hour.
The authorities in Zurich, Basel, Bern and Lausanne switched off the floodlights bathing many monuments, bridges, churches and public buildings between 8.30 and 9.30pm.
Zurich officials used the international campaign, organised by the environmental organisation, WWF, to promote the fact that residents voted in favour last year of setting as a goal reducing each person's energy use to 2,000 watts a year – about a third of current consumption.
The Basel authorities emphasised that shutting off the lights for an hour would do little to save energy, but would act as a reminder of the need to take action immediately.
Lausanne, as well as the nearby towns of Nyon and Yverdon-les-Bains, invited the local population also to take part in the campaign.
More than 80 countries took part this year, including newcomers China and Singapore.
In the Vatican, the dome of St Peter's Basilica went dark, as did Egypt's Great Pyramids, the Eiffel Tower in Paris and New York's Empire State Building.
WWF, which started the event in Sydney in 2007, was hoping to get one billion people involved this year.
swissinfo with agencies