Vianen is a city and a former municipality in the central Netherlands, in the province of Utrecht. It is located south of the Lek river. Before 2002 it was part of the province of South Holland. Vianen is made up of a historic town centre that dates back to the medieval period and was once surrounded by a defensive wall and moat, as well as more extensive modern housing developments to the east, south and southwest and an industrial and commercial area.