In Barcelona, anyone passing by is invited to lend some stationary bike exertion to a cause—lighting a tree to create a true Christmas miracle. It's a neat idea, if you believe it.
Wired does not.
Like the Wizard of Oz, the workings are hidden behind a curtain. One thing we do know — there is either cheating or batteries involved. I've walked by a few times to see nobody on the bikes, but the lights still blazing.
Perhaps the tree is powered by Christmas spirit? [Wired]