For four of my books, I’ve had to do extensive research into castles (keeps), and the great, or grand hall, has played a major roll in each. 
Put simply, the great hall is the largest room in a castle or palace (sometimes even a manor house), and in the case of my Scottish characters, a place where the kin and kith not only dined, but entertained guests, and conducted various types of business required of a laird or chieftain.
Wedding, festivals, and dances take place in the great halls as well. In medieval times, household and clan’s members might even have slept in the hall along with the dogs.
Rectangular in shape (generally 3 times as long as wide) with a high ceiling, the great hall usually included a minstrel’s gallery and trumpeters loft, a side with windows (often
quite elaborate as seen is this image), and a dais situated at one end of the room upon which the laird and other important family and clan’s members sat.
Tapestries, weaponry, suits of armor, portraits, and stuffed trophies typically adorned the walls.
Long trestle tables and benches were used for dining, and additional benches were placed beneath the windows. The great halls was a gathering place as well. Craiglocky Keep, the castle I use as a setting in my books has over 160 rooms, and while there are parlors and drawing room, much of the social interaction of the residents takes place in the keep’s great hall.
As my books all take place in the early 1800s, I moved away from the benches for seating and have chairs instead. As you can imagine, the stone floors were a tad chilly, so straw and rushes would cover the floors in medieval times, often sprinkled with herbs such as mint and lavender. A fireplace large enough to stand inside adorned with a ornate over-mantle was used for cooking and as a heat source, though separate kitchens were also very common.
As you can see in these images, the size and opulence of the great halls were quite varied. I’ve seen the great halls at a few of England’s castles, but am very excited to visit Scotland’s castles next summer.
Have you ever set a scene in a great hall or seen one in person?
Resources:
http://en.wikipedia.org/wiki/Great_hall
http://www.medieval-castles.net/castle_architecture/rooms.htm
http://www.castlesandmanorhouses.com/life_01_rooms.htm
