The first church here was timber, put up in 860 by Ansgar, the missionary monk from Hamburg who later became its archbishop. He had King Horik I's permission to build on the south bank of the river, across from the market - a remarkable concession from a pagan king who had burned Hamburg fifteen years earlier. The locals were less accommodating. In Ribe and in Hedeby, people complained that the bells would frighten off the landvaetter, the spirits of the land, and Horik's successor closed the Hedeby church in response - though Ansgar eventually won that king round too. When his successor Rimbert died in 888 the mission collapsed and the church was burned to erase the memory of the foreign religion. Ribe became a diocese in 948 under its first bishop, Leofdag, whom a housecarl speared to death while he forded the river that same year. He was never canonised, but Ribe revered him as a saint until the Reformation, and his remains ended up inside the cathedral.

West Jutland is sand and marsh, so the twelfth-century builders imported their material: tufa, a soft volcanic stone shipped north from Germany. What went up was a Romanesque basilica of half-round arches under a flat timber ceiling, modelled on the churches of northern Germany. Fire took the town and the new cathedral in 1176, and it is precisely because the fire failed to finish the job that Ribe is what it is today: the surviving stonework was repaired rather than replaced, and the additions came in large red brick, a material nobody in Denmark had used before. The nave gained double aisles, and Gothic vaulting replaced flat ceilings in places. The great south doorway belongs to this period: a relief of Christ taken down from the cross, beneath a triangular tympanum of the Day of Judgement carved some fifty years earlier - among the largest Romanesque granite reliefs anywhere. Everyone calls it the Cat's Head Door, for the two lions crouched at the base of the flanking columns.

Two Danish kings lie here, and neither died peacefully. A chieftain remembered as Sorte Plov - Black Plough - killed Erik II, called Emune, at the Urnehoved assembly in July 1137, avenging a relative Erik had executed. Erik had made a great many: he had put his own brother Harald to death along with ten or eleven of Harald's twelve sons, and earned the name Bloody Erik for it, though later chroniclers preferred Emune, roughly "the one who ought to be remembered." His burial raised the cathedral's standing considerably. Christoffer I went more quietly and more strangely. On 29 May 1259, deep in a dispute with the Archbishop of Lund over whether a king had authority over churchmen, he died suddenly after drinking communion wine that rumour said an abbot had poisoned. He too was buried in Ribe, and his gravestone survives.

The tower that replaced the one lost in 1283 was built on a different scale, and for a different purpose. Borgertaarnet, the Commoners' Tower, was finished in 1333 at 62 metres under a copper spire. The church used the lower floors; the town used the upper ones, as a record archive and a lookout. During the Danish-Swedish wars eight cannon were hauled to the top, and in 1644 they fired on Swedish ships. Then in 1594 this tower partially collapsed too. It was rebuilt ten metres shorter, with no money left for a spire, and has been flat-topped ever since. Two hundred and forty-eight steps take you to the viewing platform, and the reason to climb them is the horizon: marsh, dyke and the Wadden Sea. On the night of 11-12 October 1634 that sea came inland in the surge Danes call the Great Drowning. Thousands died along the marsh coast. A mark on the pillar by the pulpit shows where the water stood inside the cathedral.

The Reformation reached Ribe in 1536; the cathedral closed, the monks were turned out, and the building was left to neglect until Hans Tausen arrived as its Lutheran bishop in 1542 - his statue stands at the foot of the Maria Tower. By 1560 the last Catholic altars and statues were gone and the medieval wall paintings plastered over. Nineteenth-century restorers stripped the plaster and destroyed most of what it had protected; a Virgin and Child in the nave and a St George in the north transept are among the few frescoes left. The most contested change came last. Across the 1980s the COBRA painter Carl-Henning Pedersen filled the apse with mosaics, glass mosaics and frescoes in his unmistakable idiom of floating figures, suns and animals. The row began before a tile was laid. A public exhibition of the designs drew ten thousand visitors, half of whom approved, and the parish council went ahead. Denmark's churches have been commissioning living artists ever since.