I'm writing a story and need a word to describe the throne room. It's absolutely enormous with extremely high ceilings and columns instead of walls. For scale, the room is big enough for 5 or 6 larger dragons to rest comfortably. I was thinking about describing it as a pavilion, but that sounded a bit too serene I guess.

Edit: This is the actual description in the story - It was a vast open space with a soaring roof. Columns supported the ceiling in lieu of walls, granting Dorian a breathtaking view of the mountains surrounding the castle.