"The New French Hacker-Artist Underground" by Jon Lackman. The people in this true story make me want to hop on a plane tomorrow just to meet them. They are known as UX (think underground experiment) and they are highly skilled artisans who hang out in the old tunnels under Paris. Their hobby is secretly restoring the many historical treasures that go neglected in their great city. My favorite project that they took on was sneaking into Paris' Pantheon to restore its 19th century Wagner clock. They also host their own film festivals down there. But read the article - they tell their story much better than I do.
Here is a short video about the clock: