The subject of this article originates from non-canonical sources. To find out about what is considered "canon" see LOTR:Canon.
Gallery of Kings was a Dwarven hall and gallery at Erebor.
In The Hobbit: The Desolation of Smaug, Thorin and Company evade the dragon as he attempts to kill them and are eventually split up in the chaos, with Thorin commanding them all to make a run for the Gallery of Kings. Smaug spots Bilbo and chases after him, and he is quickly overrun by the dragon once they reach the Gallery of Kings. Smashing through the Gallery's wall, Smaug furiously roars that he finally understands that Bilbo and the Dwarves were aided by the men of Lake-town, and leaves to destroy the town. Bilbo cries out in protest, claiming the people of Lake-town are innocent. Smaug stops in his tracks, and cruelly expresses his pleasure in Bilbo's compassion, proclaiming that he can watch them all die.
As Smaug turns to leave again, Thorin appears atop a giant stone cast at the other end of the hall and taunts him. As the dragon reaches Thorin, the dwarf proclaims that they will have their revenge and yells out to the other dwarfs, who are revealed to be holding enormous chains attached to the stone cast upon which Thorin is standing. The dwarves pull the chains, causing the stone cast to fall apart and unveiling an enormous, freshly cast golden statue of a dwarf. Smaug gazes in awe of the statue, which suddenly explodes in a flood of molten gold and buries the dragon. However, Smaug survives the scalding gold and erupts from the molten pool, roaring that he will show the dwarves what revenge really is. He smashes through the walls of the mountain, shakes off his gold coating, and takes flight to Lake-town.
In The Hobbit: The Battle of the Five Armies, Thorin and Company return to Gallery of Kings and remain for a while. Later when Oin, Bofur, Fíli and Kíli arrive at Gallery of Kings, Bilbo comes up and warns them. Then, after Thorin threatens to kill Bilbo and Dwalin, he goes to there alone. He starts to think he is similar to his grandfather, Thrór. He is disappointed and saw a shadow of himself falling down into the melted golden floor. He screams and throws his crown on the floor. Then, he determined to join the Battle of Five Armies.