A sun-deprived village in the Italian Alps has come up with a novel solution to fix the problem - by installing a giant mirror.
Viganella marked its "day of the light" on Sunday
The mirror - an eight-by-five metre (26x16ft) sheet of steel - was placed on a nearby peak to reflect sunlight onto Viganella's main square below.
The computer-operated mirror will now be constantly following the sun's path.
Viganella sits at the bottom of a steep valley, and surrounding mountains cut off direct sunlight during the winter.
The towering mirror was installed on Sunday.
"It wasn't easy," Village Mayor Pierfranco Midali told Italy's Ansa news agency.
"We had to find the proper material, learn about the technology and especially find the money," he said.
The project cost some 100,000 euros (£67,110) and was financed by the regional authorities and a bank.
Viganella's problem is that it was built at the bottom of a very steep-sided Alpine valley, right up against the Swiss border.
The mirror is remotely controlled by a computer
The southern side of the valley is so sheer that on 11 November the sun disappears and does not reappear until 2 February.
Not a single ray of sunlight falls on Viganella in the weeks in between.
"It's like Siberia," one of the village's nearly 200 residents has said.
However, the south-facing slopes to the north do get sunshine just a few hundred metres above the village.
So the mirror was mounted on the mountainside to reflect sunlight into the village's main piazza.