alta's got the shack attack locked down. all their smoke shacks are perched above some of the nastiest & steepest terrain on the mountain, so when you get all bake faced you get to shred some sweet lines right after. although i think the eagle's nest shack collapsed last year under the weight of our epic powder accumulations.
copper mountain has an abandoned mine cave. I haven't tried to go in though of course because it's extremely sktch and the air is probably deadly, but it would be cool
I've found two structures at Gore, along with a few cave/stone places...along with this 10x10 rock outcropping you've got to climb up an ice face to sit on...and then above you is another 15 foot rock face. Sooo dope.