Imagine a city where a rush-hour backup might involve just a few cars, and the air is clean because just about everything runs on zero-carbon energy. That's the goal for the Swedish capital, Stockholm.
The Swedish warship Vasa sunk in the 17th Century on its maiden voyage. It keeled over and water rushed in, killing 30. New research has found that specific flaws in the ship's design probably sent it to its early, watery grave.