I have been living a long time in Paris itself (Pharmacy studies, plus moved back in 2012), including some time not too far from the catacombes's entrance, but I have never visited them, LOL. The appartment I sold last year was nearby an old train track that used to go around Paris to carry in and out diverse manufacturing / chemical parts and goods, and that track makes for a path still very much used today for illegal entrance in the catacombs (for feasts, drug deals, off the grid living...). I would do the regular visit, but the illegal one? Uh no, I am too much of a scaredy cat for that (plus it can really be dangerous).