HIghclere Castle isn't really a castle.......it's a Georgian manor. Remodeled in the 1800's by Sir Charles Barry, who was the architect for the British Parliament buildings in London (and you can see the similarities!), it looked very different before the remodel.
In person, the house seems smaller than it does in the series-----they must be shooting with a reeeaaalllllly wide lens for sure. It's big, but not massive-----but quite lovely. You get to tour part of the interior, and all of the exterior-----highlights are Sybil's room (not needed any longer, I guess!), Edith's room, and the room occupied by Mr. Pamuk before his unfortunate demise.
Mary's room, and Cora and Robert's rooms don't exist at Highclere---they are all offsite in the studio. That said, the salon on the first floor, the staircase, and the library are spectacular. It makes me want to go back and watch the entire 3 seasons, just to look at the rooms and the grounds.
It's fun to go around the back of the building----Sir Charles didn't reface the entire building, so you can still see the original Georgian brick facade----it looks unfinished from the back.
No Maggie Smith sightings.
Enjoy the photos: