|The following is based on Van Buren and has not been confirmed by canon sources.|
A large and somewhat boring (both in terms of fights—there are none—and in terms of appearance—the interior is pretty drab) set of caves with stalagmites, stalactites, and a few small pools of runoff trickled in from the ceiling. The tribe uses this place to store water, ice (when they save some from the winter), firewood, jerky, and other durable goods.
They also can retreat into here if they're attacked by an overwhelming force or extreme weather, though they've never had the need to do so yet. The entrance is guarded. There's a section in the back that a high-PE and high-[SKILL] player character can notice that would be easy to open up with some explosives, and behind it is another place where they can do some silver mining.