In the centre of Copenhagen is a small, canal-encircled island called Slotsholmen, which serves as Denmark's governmental seat. It was here in 1167 that Bishop Absalom constructed a small fortress within a harbourside village to try and stifle regular raids by the German Wends on the east coast of Zealand, thereby laying the foundations for the future capital of Denmark. The fortress inflated the village's sense of self-worth, causing it to grow significantly and to adopt the name Kømandshavn (Merchant's Port) - the moniker was eventually shortened to København.

The fortifications built by the bishop were destroyed during an attack on the town by ransackers from northern Germany in 1369 and work on a new defensive structure, Copenhagen Castle, began seven years later. The city's fate as the capital of Denmark was secured in 1416 when the reigning monarch, King Eric of Pomerania, moved into his sturdy new castle quarters. Grand Renaissance buildings such as the Rundetårn (Round Tower) - established as an observatory and still regularly used for that purpose - and Børsen, home to Denmark's stock exchange, were added in the first half of the 17th century by the aesthetically minded ruler Christian IV.

Copenhagen grew swiftly in size and population, and by the beginning of the 18th century had around 60,000 people living within its confines. The next 100 years weren't kind to the burgeoning capital, however. By 1711 nearly one-third of the population had died from bubonic plague, and a pair of fires (in 1728 and 1795) turned large areas of the city, including most of its wooden buildings, to ash. To top it all off, in the midst of the Napoleonic Wars in 1807, Britain's Admiral Horatio Nelson decided he'd had enough of Denmark profiting from wartime foreign trade, and of rumours that the neutral Danes were considering putting their naval fleet at Napoleon's disposal, and ordered a savage bombardment of the city. Much of Copenhagen went up in flames (again) and the British rubbed salt into the wound by confiscating the entire national fleet.