Aude department, Languedoc
The Aude is perhaps the most genteel, relaxed of Languedoc Roussillon's 5 departments. It lacks the dramatic landscape of the Pyrenees-Orientales or Herault. Instead, it is carpeted with vines and more vines, which stop at about Carcassonne, giving way to soft farmland - fields of sun flowers and rapeseed.
Like the Pyrenees-Orientales, the department of the Aude is Cathar country, with some of the most famous Cathar ruins located here. The castles of Queribus and Peyrepertuse sit on high cliff edges overlooking gorgeous valleys and the Pyrenees. The most famous historical monument, of course, is the spectacular (if over-restored) 'Cite' of Carcassonne.
The Aude economy is dominated by wine, with the famous Corbieres and Minervois regions pumping out increasingly good quality wine year after year.
The Aude climate is mostly Mediterranean - with temperatures dropping slightly west of Carcassonne, and higher rainfall too.
The Aude lacks big cities. Both Narbonne and Carcassonne could be accused of being a little sleepy. But at least their relatively smallness has spared the region the relentless build-up found in Herault and Gard.
I think the jewel in the Aude's crown isn't the Cite at Carcassonne, but rather the Canal du Midi, which winds its beautiful way from Carcassonne to the sea, lined with Plane trees and dotted with pretty stone bridges. On a hot summer's day, it's cool and green and peaceful (even despite all the boats), and the perfect place for a walk or bicycle ride.
Like most of Languedoc, the coastal regions of the Aude get very crowded in summer. They're also relatively expensive property-wise, with people clamouring to buy apartments near the Aude's enormously long and straight beaches. Much of the Languedoc coast here is pretty ugly, with Leucate, La Franqui and Bages being Aude's notable exceptions.