Numedalslågen in the context of Southern Norway

Vestfold (pronounced [ˈvɛ̂stfɔɫ] ) is a county and a current electoral district in Norway. Located on the western shore of the Oslofjord, it borders Buskerud and Telemark counties. The county administration is located in Tønsberg, Norway's oldest city, and the largest city is Sandefjord. With the exception of the city-county of Oslo, Vestfold is the smallest county in Norway by area.

Vestfold is located west of the Oslofjord, as the name indicates. It includes many smaller, but well-known towns in Norway, such as Holmestrand, Horten, Åsgårdstrand, Tønsberg, Sandefjord, Larvik and Stavern; these towns run from Oslo in an almost constant belt of urban areas along the coast, ending in Grenland in neighbouring county Telemark. The river Numedalslågen runs through the county. Many islands are located at the coast. Vestfold is mostly dominated by lowland and is among the best agricultural areas of Norway. Winters last about three months, while pleasant summer temperatures last from May to September, with a July average high of 17 °C (63 °F).

Kongsberg (Norwegian pronunciation: [ˈkɔ̂ŋːsbær(ɡ)] ) is a historical mining town and municipality in Buskerud county, Norway. The city is located on the river Numedalslågen at the entrance to the valley of Numedal. Kongsberg has been a centre of silver mining, arms production and forestry for centuries, and is the site of high technology industry including the headquarters of Norway's largest defence contractor Kongsberg Gruppen.

Kongsberg, formerly spelled Konningsberg (lit. "King's Mountain"), was developed as a mining city on the basis of the Kongsberg Silver Mines, founded by and named after King Christian IV of Denmark and Norway in 1624. The king invited German engineers and other specialists from Saxony and the Harz region to help build the mining company. As a mining city, Kongsberg had a distinct urban culture that contrasted with its surroundings, strongly influenced by the traditions of mining communities in Germany and where the German language was extensively used in mining business and for religious services. In the first years nearly half of the city's population were German immigrants, and the majority of the engineers and executives were German immigrants and their descendants well into the 19th century, becoming a distinct social class called mining families that formed the educated social elite of Kongsberg in contrast to the Norwegian farming population; the first Nobel laureate in economics Ragnar Frisch belonged to such a Kongsberg mining family. By the 18th century Kongsberg was Norway's second largest city, second only to Bergen. Kongsberg was one of Norway's two privileged mining cities and thus formed a special mining jurisdiction (Bergstad), and only became part of Buskerud county in 1760. On 1 January 1838, the new national law, creating local governments, made Kongsberg a municipality. The rural municipalities of Ytre Sandsvær and Øvre Sandsvær were merged into the municipality of Kongsberg in 1964. Kongsberg gradually lost importance to other cities in the 19th century, particularly to the rapidly growing capital of Christiania (Oslo).

Larvik is a town/city in Larvik Municipality in Vestfold county, Norway. The town is the administrative centre of the large municipality which stretches inland for over 50 kilometres (31 mi) from the coast. The town is located near the Skaggerak coast, wedged between the Larviksfjorden to the south, the lake Farris to the north, and the river Lågen along the east side of the town. The town was established in 1671. The town became a self-governing municipality on 1 January 1838 under the formannskapsdistrikt law. The town remained self-governing until 1 January 1988 when it was merged with the neighboring town of Stavern and three neighboring rural municipalities to form a much larger Larvik Municipality.

The 15-square-kilometre (3,700-acre) town has a population (2022) of 26,821 and a population density of 1,791 inhabitants per square kilometre (4,640/sq mi). This means over half of the population of Larvik Municipality lives in the city, the rest live in the much more rural areas of the municipality.