Ben’s House
I don’t know if this has been brought up before, but I’ve been wondering for a while about the hidden room in Ben’s house, that he disappeared into to summon the smoke monster after Alex was killed, and then we saw it again in ‘Dead Is Dead’, when he summoned the Smokester and it didn’t show.
They were obsessed with the cave systems and built all of their stuff around them. I think it’s seasonable to say that they at least had some interest in the cave and the carvings on the walls.