I always feel warm and fuzzy when the Christmas tree gets put up, but it's definitely not because I'm sweating from pedaling bikes to keep the decorations glowing. I'll leave that to these crazy folks in Copenhagen.
The 700 LED lights on this particular city's Christmas tree are not connected to any sort of traditional power outlet, instead relying completely on volunteers pushing the pedals of some stationary bicycles. It's certainly environmentally friendly, but will they seriously manage to consistently keep 15 people working out? [CNET]