Wadden Sea National Park was designated a Danish national park on 17 January 2008, effective 2010. The Wadden Sea National Park is by far the largest of Denmark's national parks outside of Greenland and covers the Danish part of the Wadden Sea from Ho Bugt to the German border, and includes the islands of Fanø, Mandø and Rømø, as well as Skallingen, the Varde Å valley, and many of the marshlands of Tjæreborgmarsken, Ribemarsken, Margrethekogen and De Ydre Diger in Tøndermarsken.