What makes a setting Gothic?

I think that darkness and shadow plays a key part in making a setting Gothic, because it adds a sense of the unknown. To use an example, your own room; in the daytime it's lovely and it's your room and there's nothing sinister about it, but then you turn the lights off, add in it taking more time than usual to fall asleep and it suddenly becomes a Gothic setting, where the sound of your own breathing becomes something that makes you jump a mile and start thinking about how you really should stop putting clothes on top of things because it looks spookily like a ghostly figure sitting in the chair. Then you turn the light back on and everything seems totally fine.

Another thing that makes a Gothic setting is the vulnerability of the people that are in the setting. For example, someone with a broken leg, dragging themselves to the nearest escape while the walls are slowly caving in would be seen as more vulnerable than someone fully capable of running through and being totally fine at the other end, and therefore more Gothic because there is an element that makes the reader uncomfortable; there is less chance of the guy with the broken leg getting out and so reading about his struggle to escape puts the reader more on edge and therefore makes the Gothic setting successful.

Adding children, or innocence. For example, in Insidious it is the child who is trying to be possessed by the demons etc not the father, even though the father has the same abilities as the child (I'm not taking the end into account because it was at the end and not the bulk of the film) which then plays on the feelings of the audience because children are seen as innocent, and what is trying to possess the child is the complete opposite, and so it has the attempted corruption of innocence, paired with the grey setting and dark-ish house which makes it Gothic.