The Aude is an authentic region with little population offering large natural parks like the regions of the Corbières (3000 km²)(1) and the Montagne Noire(2) where you can walk for hours without meeting anyone (nature is free for everyone and not fenced around), the protected areas of the coast, the lagoons et and the salt lakes of Bages till Port La Nouvelle(4), where you are face to face to flamingo's and will discover the wild vegetation containing many protected species, and the rocky coast of La Clape and Leucate
Famous are the Gorges de Galamus(3) and the "défilé de la pierre-lys" in Quillan, the grots of Clamoux, Cabrespine and Limousis (5) bird reserve and observation in the lakes of Bages, Sigean and Leucate, the Africain reserve of Sigean (6) and the dinosaurs museum in Espéraza (7)

Links+info

(1) http://www.tourisme-corbieres-minervois.com/
(2) http://www.audetourisme.com/
https://www.aude.fr/jai-envie-de-profiter-de-la-nature
(3) close to the castle of Peyrepertuse you will find impressive canyons created by the river Agly over a 4km distance, magnificent views and natural basins are a welcome refreshment in summer period, visit also the Hermitage, access by a foot path.
http://www.gorgesdegalamus.fr/
(4) the lake of Bages, take the magnificent road between Peyriac and Bages, in Peyriac several paths between the lakes, the beach of Doul, and the isle "L’île St Lucie" in Port la Nouvelle
(5) http://www.audetourisme.com/fr/decouvrir/espaces-naturels/grottes.php
(6) http://www.reserveafricainesigean.fr, a reserve where animals are left free within the park, visit by car, a total park of 300Ha and 3800 animals coming from the 5 continents
(7) http://www.dinosauria.org, here you can find the real scelets and eggs of dinosaurs, in summer period you can visit the archaeological site.

You will find more info under the section sport