Albi Cathedral, formally the Cathedral Basilica of Saint Cecilia (French: Basilique Cathédrale Sainte-Cécile d'Albi), is the most important Catholic building in Albi, France, and the seat of the Roman Catholic Archbishop of Albi (in full, Albi-Castres-Lavaur). First built as a fortress in the aftermath of the Albigensian Crusade; begun in 1287 and under construction for 200 years, it is claimed to be the largest brick building in the world.