It was founded in 1270 on the Northern shore of Erie Vatn next to the Afturbrándjórd River during the slow Vinlandic conquest and settlement of the Hafsvaedaland. It took its name from a location known as Tkaronto by the local tribes, meaning something like 'place to catch fish'. The early pre-conquest traders had used the area as a portage point over to Karegnodí Vatn while a long spit protected a natural harbour from heavy storms.
As the main landing port ('the Key') for expansion in the Hafsvaedaland Karantóborg quickly grew in size and importance. Its markets attracted much of the produce of Hafsvaedaland. Although nominally owned by the Earls of Kyrejya its Lord-Marshalls were soon independently wealthy and their efforts in keeping the peace and expanding Vinlandic territory was recognised by the crown with grants of extensive land.
The city was the scene for much of the disruption caused by the Peasant's Revolt of 1367-68 (see Snaedis II). Protesting taxes and lack of Christian preachers in the countryside two large bands of peasants under Jakob Ívarsson and Mattias Massaikasson gathered arms and raided various towns and villages before occupying Karantóborg. The city too had its own gripes; for it had been repeatedly denied certain rights by the Lord Marshalls and gladly let in the rebels whereupon they quickly denuded the churches of their finery and executed the highest clerics they could lay their hands on. However city was increasingly put out by the rebels behaviour over the winter and when Snaedis II offered amnesty in the spring they quickly accepted, arresting the leadership of the revolt.
During the reign of Jabokina II Karantóborg's already extensive walls were massively improved, creating 'the finest fortress in Leifia'. However the works may have been over-enthusiastically planned and as legend would have it were designed by an Italian architect who refused to leave his native city and simply drew up the plans to get rid of the insistent . Enclosing around 4 km.sq., and with the walls extending around the harbour-spit, the city would not 'spill over' until the 20th century as there was ample space for the population within the walls. In fact it was quietly realised that actually defending such a massive fortress was nigh-on impossible. This was most blatantly shown in 1835 during the Vinlandic-Eriac War when the Eriac fleet brazenly entered the harbour and shelled Karantóborg from within for several days, killing hundreds and starting several fires. As it was, just before the Reformation in 1520, the walls encompassed three monasteries with their own small farms, 32 churches, a 'forest'; jointly owned by the crown and the Lord-Marshall, two hospitals, several lavish guildhalls, numerous port-side warehouses, the Marshall's grand manor house and some 70,000 people. This tended to mean the streets were widely spaced which in turn reduced the damage done by fires.
The city was regularly hit by plague keeping the hospitals and churches busy but thanks to its proximity to the farmlands of the Hafsvaedaland the populace rarely succumbed to famine. During the Reformation it was a 'first point of call' for many European Protestants and Non-Conformists fleeing their homelands and the city acquired a reputation for being progressive and free-thinking. This was momentarily suppressed during the reactionary reign of Freydis III in the mid 1600s but the creative and societies simply lay dormant and soon resurfaced.
Long a trading city moving the agricultural produce of the Hafsvaedaland off to other markets the growth of industry, especially paper, iron, steel and machinery in the late-19th and 20th centuries has attracted thousands out of the countryside and meant the city rapidly expanded. The city is well-noted for its literary scene and it rivals Fjallasay for cultural capital of Vinland.
The annual carnival held for a week starting on 1st April is, as many Vinlanders will admit, a blatant copy of Venice's much grander carnivale. While the well-to-do citizens of Karantóborg have generally held feasts to celebrate the end of winter since the Late Medieval times the current institution dates from the 19th century. Queen Kristjana VII had attended the Venice carnival in 1855 as a princess and, as was the fashion brought many European artifacts back to Leifia, including carnival masks. The costume balls, firework parties and parades she helped develop in part to celebrate the reconstruction of the city after its 1835 bombardment have encompassed a far wider audience than those previously had and the growing industrial populace of Karantóborg embraced the festivities as a way of celebrating the end of winter.
Karantóborg is the capital of Sud-Hafsvaedaland Fylk and the Fylkthing sits in the city. The Fylkthing is regularly bogged down in cession movements from various parts of the Fylk, indeed many would like to see Karantóborg itself becoming a separate Fylk. It is predicted to overtake Fjallasay as Vinland's largest city this century and many propose moving the capital and Althing to Karantóborg rather than it remain in the somewhat isolated Isafjordhur.