What is "gamleborg"

Gamleborg, also known as Gamleborg Viking Fortress, was the first fortress on the Danish island of Bornholm. Built around 750 AD, it was the seat of the kings of Bornholm during the Viking age (750–1050) and early Middle Ages (1050–1150). The massive fortress is long from north to south and wide from east to west, with gates to the north and southwest. Around 1100, significant alterations were made and it was reinforced, but it was abandoned soon afterwards in favour of Lilleborg Castle, roughly to the northeast.