Copenhagen Christmas tree powered by cyclists

The giant Christmas tree in Copenhagen City Hall Square is a mass of hundreds of lights… but only while people are pedalling.

That's because in a bid to be environmentally friendly, the lights are connected to a selection of exercise bikes which generate power as they are pedalled.

As peoples legs spin they light up the tree - and burn a few calories while they're at it.

It is predicted the alternative way of lighting up the Christmas tree will save the environment a total of nine tonnes of CO2 compared to the traditional way of powering the lights.

But isn't it hard to be full of Christmas sprit if you are panting for breath?