The huge brick fortress-like cathedral at Albi is worth a visit. It has an atmosphere of evil which is interesting to experience. It was built after the Cathars were crushed, to emphasise the dominance of orthodoxy over the region, it is huge and ugly and it includes a vast interior picture of souls being tortured in hell, which I think is extraordinary to see.
A lot of people (including me) come away from that part of the world with strong and not always entirely rational feelings. For example I'm pretty sure Kate Mosse wrote Labyrinth (though I haven't read it) in the grip of that feeling, and there are others. Darkmans by Nicola Barker has a character obsessed with Albi cathedral. Arthur Guirdham took it literally, and thought he and his friends were reincarnations of people who had lived there.
I know some people think events imprint on places. Or it may be that events leave a strong cultural residue. There's a recognised Jerusalem syndrome, which affects people from cultures for which Jerusalem is highly significant. Is that significance literally imprinted in the bricks and mortar of the place? Or (I suspect) entirely in the mind? And the same but for a different group of types, in whom I include myself, for Albi and Carcasonne.
ETA - and I see there's a Stendahl syndrome, which is based on Florence.