Construction of the cathedral began in 1247 and was only finished in 1880 after an interruption that lasted more than 300 years. Ribbed vaults and flying buttresses, the film explores the architectural vocabulary of the gothic style and its building methods. It reveals the most recent contribution of metal to architecture. It demonstrates how this cathedral that embodies German unity is at the same time archetypal of the Gothic style and of a 19th century building.