On a hill above the River Aude, the Romans built the first walls of Carcassonne. In the 12th century the Trencavel viscounts built the castle, the Château Comtal, and the town became a centre of the Cathars, a Christian movement the Church declared heretical.
In 1209 a crusade against the Cathars besieged Carcassonne and took it. The kings of France then added a second, outer ring of walls, making the Cité almost impossible to capture: about three kilometres of ramparts with 52 towers.
By the 19th century the walls were crumbling and the government planned to pull them down. Local people protested, and from 1853 the architect Viollet-le-Duc restored them, adding the pointed slate roofs we see today. The Cité became a UNESCO World Heritage Site in 1997.
