Roskilde (rôsˈkĭlə) [key], city (1992 pop. 40,928), capital of Roskilde co., E Denmark, a port on the Roskilde Fjord (an arm of the Isefjord). Manufactures of this industrial city include processed food, liquor, machines, leather goods, and pharmaceuticals. One of the oldest Danish cities, Roskilde was the capital of Denmark from the 10th cent. until 1443, when it was replaced by Copenhagen (which had been chartered by the bishop of Roskilde). The city was the country's ecclesiastical center from 1020 to 1536, when the see of Roskilde was suppressed during the Reformation. Subsequently, the city declined rapidly. The Lutheran bishops of Sjælland resided at Copenhagen, but their cathedral continued to be that of Roskilde. It is a magnificent edifice (late 12th cent.) containing about 40 royal tombs, including those of most Danish kings. The commercial prosperity of Roskilde revived in the 19th cent., and in 1923 it again became an episcopal see. By the Treaty of Roskilde (1658) Denmark ceded its lands in S Sweden to Charles X of Sweden. Roskilde has a museum of Viking ships, and nearby is an atomic research center.