Dragons, Trolls, Men, Orcs, Dwarves, and (presumably) Wargs all had penchants for accumulating treasure. In all likeliness, the items procured from plundering would be taken and hidden in holds and hidden vaults. Smaug's lair in the Lonely Mountain, Moria, and the troll den mentioned in The Hobbit would all serve as illustrations of this.
Portrayal in AdaptationsEdit
In The Hobbit: An Unexpected Journey, Thorin's Company had hid some chests of treasures inside the ground of the Trollshaws. In The Hobbit: The Battle of the Five Armies, Bilbo and Gandalf had digged it out from the ground, as an echo to the first film.