Catharism was a Christian movement in the 12th-14th centuries that varied from the Catholique principles in some basic areas, including good and evil gods, and abstinence from wealth and sensual pleasures.
Catharism began in the Languedoc region (now Occitanie) of southern France in the 11th century, where the name was first used. Adherents were also called Albigensians, from the city of Albi where the movement began.
Our interest here in Catharism and the Albigensian Crusade is the cultural and architectural remnants across southwestern France, especially Cathar castles, abbeys and walled towns.
Pope Innocent III attempted to halt the Cathar movement with missionaries to the region and by influencing local authorities. When this turned out to be a resounding failure, the Pope turned to force, beginning the Albigensian Crusade to end Catharism the hard way. The Albigensian Crusade, or Cathar Crusade, lasted for 20 years, from 1209 to 1229. Although started by the church, the crusade was executed mainly government troops to bring independent regional areas under control of the French crown.
There are around twenty-some Cathar Castles remaining in the South of France. The validity of a castle being Cathar varies according to different criteria and different experts. A castle could have been destroyed completely after the 14th century and rebuilt in the following Medieval centuries; many consider that site to be Cathar even though the original castle is no longer there.
Many of the castles are "original", but little remains but low ruins on a high peak. The size and grandeur of the Cathar Castles varies from these small rocky ruins up to the complete walled town of Carcassonne Walled City.