The episcopal city, situated in the center of the actual city, around the cathedral, was added to the UNESCO list of World Heritage Sites in 2010. The first human settlement in Albi was in the Bronze Age (3000-600 BC). After the Roman conquest of Gaul in 51 BC, the town became Civitas Albigensium, the territory of the Albigeois, Albiga. Archaeological digs have not revealed any traces of Roman buildings, which seems to indicate that Albi was a modest Roman settlement. In 1040, Albi expanded and constructed the Pont Vieux (Old Bridge). New quarters were built, indicative of considerable urban growth. The city grew rich at this time, thanks to trade and commercial exchanges, and also to the tolls charged to travelers for using the Pont Vieux. In 1208, the Pope and the French king joined forces to combat the Cathars, who had developed their own version of Christianity (a heresy considered dangerous by the dominant catholic Church). Repression was severe, and many Cathars were burnt at the stake throughout the region. The area, until then virtually independent, was reduced to such a condition that it was subsequently annexed by the French Crown.
After the upheaval of the Albigensian Crusade against the Cathars, the bishop Bernard de Castanet, in the late 13th century, completed work on the Palais de la Berbie, a Bishops' Palace with the look of a fortress. He ordered the building of the cathedral of Sainte-Cécile starting in 1282. The town enjoyed a period of commercial prosperity largely due to the cultivation of Isatis Tinctoria, commonly known as woad. The fine houses built during the Renaissance bear witness to the vast fortunes amassed by the pastel merchants.
Albi has conserved its rich architectural heritage which encapsulates the various brilliant periods of its history. Considerable improvement and restoration work has been done, to embellish the old quarters and to give them a new look, in which brick reigns supreme.