The lights went out in Reykjavik on Wednesday night to give people a chance to enjoy one of the night sky's most impressive spectacles - the Aurora Borealis.
Reykjavik council announced that street lighting would be switched off for an hour in the city centre and several other districts from 22:00 local time, in order to cut out the light pollution that can hamper sky-watching. It also encouraged the capital's residents to join in by turning off their lighting at home.
In the event, the Northern Lights' timing was predictably unpredictable, and they didn't materialise until the end of the black-out period, so the council extended it to midnight, Morgunbladid newspaper reports.
The city has witnessed some spectacular displays in recent days, as this video by astronomy educator Saever Helgi Bragason shows. It's thanks to the Earth being in the path of the solar wind - a stream of charged particles escaping from the Sun. "It's quite similar to a garden sprinkler, and we're currently inside a stream," Mr Bragason tells the BBC. The aurora appears when the particles interact with Earth's magnetic field and atmosphere.
"Switching off the street lights was a great gesture by the city council... I hope this will be done more often as it was very successful, especially for those who were patient enough to wait for the lights to appear," he says. "It also encouraged more people to go out and look up to the night sky, which is great!"