Cathar strong points were generally surrounded by a walled settlement - ranging from a small village to a sizable city - known as a castrum.
In relatively flat areas such as the Lauragais Plain, castles and castra were often located on nearby hills, for example Laurac, Fanjeaux, Mas-Saintes-Puelles, and Carcassonne.
In more rugged areas castles and castra were typically located on mountain tops as at Lastours-Cabaret, Montségur, Termes, and Puilaurens.
In some places, notably Carcassonne and Foix, substantial parts of the existing castles date from the Cathar period.
These five Cathar Castles are known as the cinq fils de Carcassonne, the Five Sons of Carcassonne: In 1659, Louis XIV and the Philip IV of Spain signed the Treaty of the Pyrenees, sealing the marriage of the Infanta Marie Therese to the French King.