Alphen aan den Rijn (.mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%}Dutch pronunciation: [ˈɑlfə(n) aːn də(n) ˈrɛin] ⓘ; English: "Alphen upon Rhine" or "Alphen on the Rhine") is a city and municipality in the western Netherlands, in the province of South Holland. The city is situated on the banks of the river Oude Rijn (Old Rhine), where the river Gouwe branches off. The municipality had a population of 112,587 in 2021, and covers an area of 132.50 km2 (51.16 sq mi) of which 6.27 km2 (2.42 sq mi) is water. The municipality of Alphen aan den Rijn also includes the communities of Aarlanderveen, Zwammerdam, and Boskoop. The city is located in what is called the 'Green Heart' of the Netherlands, which is a somewhat less densely populated centre area of the Randstad.