Fontana Dam

Dam in Great Smoky Mountains National Park

Built in the early 1940s to provide power for America's industrial needs during WWII, Fontana is the tallest dam east of the Rockies. At 2365ft wide, it's an engineering marvel – and all the more impressive given it was completed in just three years. Water released from the 29-mile-long reservoir (an impoundment of the Tennessee River) plunges down a 480ft tunnel to spin three massive turbines, which in turn generate enough electricity to power 290,000 homes.

A visitor center provides details of the construction – the nearby Fontana Village Resort was once the barracks for the thousands of workers brought in to build the dam. You can walk across the dam for fine photos above – indeed the Appalachian Trail goes right along the top. Even better views await at Shuckstack Tower, a strenuous, 4-mile (one way) hike from the dam.