The old city is at the Narbonne end of the town. We used the Narbonnne or eastern gate as we used the D6113 past many vinyards rather than the A9. Lovely run with little traffic.
3 Main car parks close to the gate (approx 5.8 euro for 3-4 hours). No tourist traps on exterior so it felt medieval as we entered. The toilets on left before you enter) Tourist office just to the right when inside. Beware cobbled streets throughout and lots of tourist shops inside. Restaurants are reasonably priced. The castle well worth a visit (8 euro) and information film on second floor as you go in. The entry guide was charming and cheerful - spoke good English. Great attention is being paid to the site as it was meddled with in the 1890's eg towers were turretted and domed at this point. Surprisingly very little inside in on the Cathars. Where did they come from, how did they die out etc, why were they attacked by tee Crusaders when all were Christian?). So read up before you enter.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.