Relics said to be those of the magi were taken from Milan to Cologne in 1164 by Rainald of Dassel, archbishop of the city and chancellor to Frederick Barbarossa, after the emperor had taken Milan by force. The transfer was a political act as much as a devotional one: it gave the archbishop of Cologne the bodies of the first kings to acknowledge Christ, at a moment when the empire and the papacy were in open conflict over who crowned whom.
The goldsmith Nicolas of Verdun and his workshop built a reliquary for them in the decades around 1200, in the form of a basilica in gilded silver set with several hundred antique gems and cameos, the largest such shrine in Europe. Pilgrims came in numbers the existing cathedral could not hold, and in 1248 the chapter began a new one, on the French Gothic model, expressly to house it. Work stopped in 1560 with the choir finished and a crane standing on the unfinished south tower for three centuries; the building was completed to its medieval plans between 1842 and 1880.
The shrine remains behind the high altar. Its presence gave the city an Epiphany feast of national importance, gave German households the custom of chalking the initials of the three names above a door at the new year, and left the cathedral as the reason the city was rebuilt around a church that survived the bombing of the surrounding streets in the Second World War almost alone.