Stuttgart 21: Was passiert wirklich?

11.5 billion euros. More than double the original cost. Twenty years of delay for a single train station. A tunnel system through unstable rock, thirty kilometers long, right under a major city. Stuttgart 21 isn't just a delayed train station project. It's Germany's biggest infrastructure disaster of our time. While Deutsche Bahn is stuck with six billion euros in additional costs, completion isn't expected until 2030 at the earliest. How could it have come to this?