Complex sentence: The park was founded in 1946; and in 2005, still owned by the founding family, was sold to an entrepreneur who resold the building to the city of Aalborg the following year.
Split into simpler sentences: The park was founded in 1946, and, still under the possession of the founding family, was sold to an entrepreneur in 2005. This individual sold the building to the city of Aalborg the following year.