9. The whole city is built on an advanced energy grid which monitors the output of every single switch and appliance.
The wind tunnel above (center) is fitted with LED lights designed to glow blue when residents are within their goal of using 50% less energy than a comparable settlement, and red when they are above their goal.
- It's time: Hillary Clinton and Donald Trump will face off tonight at 9 p.m. ET in the first of three US presidential debates.
- Inside the final days of the FARC, Colombia's 50-year-old rebel group, which is on the verge of signing a peace treaty with the government.
- Golf legend Arnold Palmer has died at 87. Known as "The King," his unusual style and charisma changed the game.