Gamleborg

Gamleborg, also known as Gamleborg Viking Fortress, was the first fortification 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 264 metres (866 ft) long from north to south and 110 metres (360 ft) 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 the fortification of Lilleborg, roughly 700 metres (2,300 ft) to the northeast.