Trondheim ( , , ; ), historically Kaupangen, Nidaros and Trondhjem (), is a city and municipality in Trøndelag county, Norway. As of 2020, it had a population of 205,332, was the third most populous municipality in Norway, and was the fourth largest urban area. Trondheim lies on the south shore of Trondheim Fjord at the mouth of the River Nidelva. Among the major technology-oriented institutions headquartered in Trondheim are the Norwegian University of Science and Technology (NTNU), the Foundation for Scientific and Industrial Research (SINTEF), and St. Olavs University Hospital. The settlement was founded in 997 as a trading post, and it served as the capital of Norway during the Viking Age until 1217. From 1152 to 1537, the city was the seat of the Catholic Archdiocese of Nidaros; it then became, and has remained, the seat of the Lutheran Diocese of Nidaros, and the site of the Nidaros Cathedral. It was incorporated in 1838. The current municipality was formed in 1964, when Trondheim merged with Byneset, Leinstrand, Strinda and Tiller, and further expanded 1 January 2020, when Trondheim merged with Klæbu. Trondheim has a mild climate for its northerly latitude, resulting in moderate summers and winters that often remain above the freezing point in seaside areas. At higher elevations, though, the microclimate is colder and snowier. The city functions as the seat of the County Mayor of Trøndelag county, but not as its administrative centre (which is Steinkjer). This is designed to avoid making the county administration too centralized. Trondheim is home to football club Rosenborg, Norway's most successful team, as well as Granåsen Ski Centre which has hosted the World Championship in Nordic Skiing. Names and etymology The city was originally given the name by Olav Tryggvason. It was for a long time called (), or in the Old Norse spelling. But it was also just called ("city") or, more specifically, ("the city in the district ", i.e. Trøndelag). The name Trøndelag, Norse Þrǿndalǫg, originally meant «the law area of the Trønder (people)» (literally Trønder-law). The first part is the genitive plural of the popular name þrǿndr, «trøndere», which is an old present participle of the verb þróask, «to grow» (with the same root as in «thrive»), and thus can be translated as «the strong, fertile». During the late Middle Ages people started to call the city just . In the Dano-Norwegian period, during the years as