Secret City Festival (Oak Ridge, Tennessee)
The annual Secret City Festival highlights the important role Oak Ridge played in World War II. In the 1940s, researchers there developed the top secret atomic bomb -- hence the city's nickname -- and today visitors can tour Manhattan Project sites to see where the bomb was devised. One of the country's largest World War II reenactments is also a popular draw, with roaring tanks, motorcycles, and other vintage military gear. Each June, the event draws about 20,000 people to Oak Ridge, which is nestled between the picturesque Cumberland and Great Smoky Mountains.