The merchants’ harbour on the Øresund that Absalon fortified in 1167: a bishops’ town for two and a half centuries, seized by the crown in 1417, and the Danish capital by the death of Christian I in 1481.
Copenhagen developed from a fishing village and episcopal center into the primary seat of Danish royal power during the later medieval period. Its natural harbor on the Øresund made it an increasingly important commercial and administrative center from the twelfth century.
The advantage was position rather than size. The town sat at the narrowest useful point of the Sound, on the sheltered water behind a chain of islets, where every ship passing between the Baltic and the North Sea could be watched, taxed or stopped. Everything that happened to the place for four hundred years follows from that.
Archaeology has found a town on the site from the eleventh century, two settlements beside a landing place that Latin writers called Portus Mercatorum, the merchants’ harbour — Køpmannhæfn in Danish, which is the name the city still carries.
In 1167 Bishop Absalon, granted the district by Valdemar I, built a castle on the islet now called Slotsholmen to hold the harbour against Wendish raiders. That fortification is the conventional foundation date of the city, and the castle site has been continuously occupied by the seat of Danish power ever since.
Absalon gave the town to the see of Roskilde, and for the next two hundred and fifty years Copenhagen belonged to the bishops rather than to the king — an arrangement that suited nobody once the harbour became rich. The herring trade of the Sound paid for churches, abbeys and a stone wall in the thirteenth century, and from about 1290 all traffic in and out passed through one of four gates or the harbour itself.
The crown wanted the town; the bishops held it; and the German towns wanted the Sound open on their own terms. Copenhagen was attacked repeatedly in those quarrels, which is the ordinary condition of a rich port with three claimants.
In 1369, in the settlement that followed the Hanseatic war against Valdemar IV, the league took the castle and pulled it down. The demolition was a political act as much as a military one: the fortification that controlled the Sound was to be removed rather than captured.
A new stronghold was built in the years that followed and was substantially complete by 1387. It still belonged to the bishops, and it still commanded the strait, so the underlying argument had not been settled at all.
Eric of Pomerania took Copenhagen and its castle from the bishops of Roskilde in 1417, ending more than two centuries of dispute, and made it a royal residence. His successors confirmed the choice: Christopher of Bavaria moved his court there in 1443 after his residence at Roskilde burned.
The city’s institutions followed the crown. The University of Copenhagen was founded in 1479, the administration settled in the castle, and the king’s command of the Sound toll became one of the most valuable assets in northern Europe.
Christian I’s residence and death at Copenhagen Castle in 1481 reflects the city’s role as the center of Oldenburg dynastic rule. By the late fifteenth century Copenhagen had displaced older centers like Roskilde as the effective political capital, a position it has held continuously.
Roskilde kept the cathedral and the royal graves; Copenhagen took the government, the university, the mint and the fleet. The medieval castle was rebuilt repeatedly and finally demolished in the eighteenth century, and Christiansborg now stands on Absalon’s islet, with the foundations of both earlier castles preserved beneath it.