[3] Kalundborg is mainly a trading and industrial town, but is also well known for its five-spired Church of Our Lady, which is closely associated with King Valdemar I and the Archbishop Absalon.

Kalundborg is at latitude 55°41′N, longitude 11°6′E, about 110 km (68 mi) west of Copenhagen on the island of Zealand (Sjaelland).

Kalundborg Municipality has approximately 20,000 inhabitants, and its network is the most published example of Industrial Symbiosis.

The history of Kalundborg Industrial Symbiosis activities began in 1961 when a project was developed and implemented to use surface water from Lake Tisso for a new oil refinery, to save the limited supplies of ground water.

The material exchanges in the Kalundborg region include: conservation of natural and financial resources; reduction in production, material, energy, insurance and treatment costs and liabilities; improved operating efficiency; quality control; improved health of the local population and public image; and realisation of potential income through the sale of by-products and waste materials.

[11] The Northwest Line (1874) connects Kalundborg with Holbæk and Roskilde and the rest of the Danish rail network.