It’s been there since earlier this year, but I only recently found out about it: in the Oosterpark there is a Fantasy tree with fairytale lights. The special thing about it is that the energy for the lights is being generated by the joggers and runners in the city! How cool.
You don’t neccisarily have to run in the Oosterpark to participate, just get a freeĀ special relay rod (baton) here and when you carry this while running anywhere in the city you contribute to the lighting of the Fantasy Tree. That way you’re not only improving your own condition, but also helping out the environment. Nice!