'Downton Abbey': Rare Behind-the-Scenes Look

"Nightline" spent time with the cast on set at Highclere Castle -- a real castle in Hampshire, England, where the show is filmed -- during the taping of Season 3, which premieres in January. Shown here, from left to right, ABC correspondent Nick Watt, "Nightline" producer Victoria Thompson and "Nightline" coordinating producer Melinda Arons standing outside of Highclere. (ABC News)