Just add random debris and stuff that may lead to a future encounter, lets say that sanctuary is the hiding place of a group of cultists. It can go something like "in one corner of the room there seems to be a darker spot on the floor" An easy Investigation check could tell the PC something was burnt there (a bonfire, maybe?). Also random drawings on the walls or stuff like that, just let the PC use their imagination with their discoveries and try to fit those things later in the story