Sunshine has lit up a Norwegian town in a remote, dark valley for the first time in wintertime, as mirrors high on a mountainside realised a century-old dream.

About 1,000 people, including children wearing sunglasses and with yellow suns painted on their faces, cheered when the sun broke through clouds to illuminate the main square in Rjukan.

Until now the town had been in shadow from early October to mid-March.

The German-made mirrors will now reflect the sun to the town's main square. 

The sensor-equipped mirrors, powered by solar and wind energy, will automatically adjust, following the sun, to continually shine upon the town square in the bottom of the valley.  

The project cost five million crown (€616,000) and involves three mirrors with a combined surface area of 51sq/m.

The idea itself is not new, said Steinar Bergsland, mayor of the area including Rjukan.

"A one-hundred-year-old idea is today being achieved. Congratulations to the Sun Mirror. This is a municipality where the impossible can become possible," he declared during the inauguration.

The man behind the idea is Rjukan resident and artist, Martin Andersen. He moved to the town from Paris in 2001 and said he missed the sun.

He said: ''We moved here in late summer and the sun began to disappear more and more, higher and higher on the mountain side.

"So we had to go farther and farther to get some sun. And it was then that I thought why not just reflect it back here to the town, a place where anyone can go to get some sun. That would be nice, and it couldn't be hard, I thought."

There are 3,500 inhabitants in the industrial town, which is about 175km west of Oslo.

A band played the 1960s hit "Let the Sunshine In", several women lounged on sunbeds drinking cocktails, fully dressed against temperatures of 7C, and a volleyball court was set up on a pile of sand.

The reflected sunlight, covering 600sq/m, is meant to create a meeting place for sun-starved locals and a draw for tourists.

Organisers reckon the reflected light will be about 80% as bright as the real sun.

The sun shines in the summer, when it is higher in the sky, but sets on 4 October behind the mountain and does not return until 12 March.

Similar mirrors were first set up in 2006 in the Italian village of Viganella in the Alps, which is also hemmed in a dark valley. 

Rjukan nestles in a deep valley in the shadow of Gaustatoppen, a 1,883-metre mountain that hosts a ski resort. The mirrors are on a ridge at 742 metres, about 450 metres above the town centre.

The idea was first proposed in a letter to a local newspaper by a bookkeeper, Oscar Kittilsen, in October 1913.

A few people in Rjukan are against the mirrors, reckoning they are an expensive gimmick. But almost all the locals are in favour.