At one time, the summer paradise of Marstrand was Sweden´s smallest town. Its history goes back to the 13th century when it was founded by King Håkon. The town flourished during the prosperous herring-fishing period of the 16th century. The building of Carlstens Fort, a landmark for all sailors and one of the island´s major sights, started at the end of the 17th century after Marstrand, under the Treaty of Roskilde in 1658, became Swedish. The fortress was the local jail during the 18th and 19th centuries and has played host to many a famous criminal, including "Lasse-Maja". In 1775 Marstrand became the first free port within the Nordic countries, which bestowed somewhat rights of freedom on the people of Marstrand. The unique town environment is characterised by the neo-Gothic carpentry work of its buildings and its cobbled streets. Today, Martsrand is a natural meeting place for yachtsman from all over the world. Every year several national and international regattas are held here, and in the sheltered harbour, boating holidaymakers and their crafts, vie for position in the summer sunshine.