Alphen aan den Rijn (population: 70,477 in 2004) is a town in the western Netherlands, in the province of South Holland. The town is situated on the banks of the river Old Rhine, between Leiden and Utrecht. The municipality covers an area of 57.68 kmē (of which 2.62 kmē water). It also contains the remnants of a Roman fort, called a castellum. The municipality of Alphen aan den Rijn also includes the following towns, villages and townships (links to additional info bolded): Aarlanderveen, Zwammerdam. The city is located in what is called the 'Green Heart' of the Netherlands, which is a greenbelt separating Utrecht, Amsterdam and The Hague.