Besides castles, this area also has several ancient abbeys that you can visit. I mostly stuck to the castles this trip.
I didn't go this way, but an alternate route could take you to the Termes castle.
The next castle I went to after Arques was Puilaurens. Not too far between the two.
Gorges de la Pierre-Lys
After leaving Arques, I drove through this gorge on my way to Puilaurens
Another castle ruin near to Arques, but currently off-limits to visitors for safety.
Nice tower-style castle that you can go up inside via the spiral staircase.