Our first stunning view of Carcassonne was from afar where there is a landscaped viewpoint just of the motorway. It didn't disappoint! The castle is on a huge scale and although the old cité is very pretty it is typically full of giftshops and cafés if you venture to walk around the outer walls you'll find it much more peaceful and less crowded, (April). The outer walls and the inner cité is free to wander however you will need to pay to visit the inner rooms and ramparts. Make sure you watch the video at the beginning about the history and restoration of the castle. It's in French but there are subtitles in English, French and Spanish. As others have said it can get chilly up there before spring/summer weather.
Tip- if you are visiting several castles think about buying a 'passport' card valid for a year which gives a discount on future entries, (castles listed only), and free entry for one child with each adult 'passport'. details on http://www.payscathare.org/
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.