Not sure if this is the place to post a question, but I booked flights to Carcassonne for 3 days/2 nights. As I don't want to be spending ALL the time in Carcassonne alone, is there any other highly recommended destinations where I could spend a day or so?

I'm sorry I don't know French but merci beaucoup in advance...!

You can go to Toulouse (1hr by train) or to the mediterranean sea (Narbonne, Gruissan..), it takes 30min to reach Narbonne by train. So you can easily see the beach or a beautiful city. Carcassonne is not a very big city and I don't think that it will be usefull to spend 2 days there, so maybe you could do both Toulouse and the beach instead, and just spend 1 day in Carcassonne. Btw Carcassonne is midway between Toulouse and Narbonne, so to check in an hotel here could be usefull.

Hello

Also from Carcassonne, you can get a bus tour organized by local tourism agencies to visit a lot of interesting and pleasant places in the surroundings

Have a good time in Pays Cathare
Nanar