For years, travelers through the San Gorgonio Pass have been struck by an awesome, otherworldly sight: never-ending, ever-expanding fields of windmills that harness the force of the breezes gusting through this passage and convert them to electricity, to power air-conditioners throughout the Coachella Valley. If you get a charge out of them, consider a guided tour, to understand more about this effective alternative energy source. Learn how designers have improved the efficiency of wind turbines (technically, they're not windmills), and measure those long rotors against the average human height (about 10 people could lie along one span).