Tårnborg was originally the name of a small fortified town whose fortifications were most likely constructed by Svend Grathe in the middle of the 12th century. After Svend Grathe's death, Tårnborg Castle was part of Valdemar I's crown land but lost its military importance when Korsør Castle was built. Tårnborg Castle's home farm () was from then on known as Korsør Castle's home farm. In 1458, Christian I allowed the farmers in the new town of Korsør to use the land for grazing in return for the payment of an annual fee. Korsør Castle's home farm was destroyed during the Second Northern War (1657–1660)
