This two-mile tunnel running on solar power just switched on today. It's part of the Paris to Amsterdam line and the first in Europe, promising to save a ton of energy that would otherwise be wasted during the trip.

Now Paris and Amsterdam obviously aren't two miles apart. But this thing features a 16,000 solar panel array that could power 50% of the entire Antwerp station, where the first train to pass through it departed from. Imagine if more of these popped up on other train lines. [Treehugger]