Iddefjord

Iddefjord ( or Idde Fjord; ); ) is a classic fjord with a narrow watercourse and steep natural formations on both sides. It runs along the Norwegian-Swedish border from the Singlefjord (). The Iddefjord separates the province of Bohuslän in the county of Västra Götaland in Sweden from the municipality of Halden in the county of Østfold in Norway. It opens to the Skagerrak via the Svinesund and Hvaler archipelago (a cluster of classic skerries). The outermost stretch is called the Ringdalsfjord (), but from the point where it makes a sharp bend and further south, it is called the Iddefjord. Like several other fjords, it was named after a part of its coast, in this case the parish of Idd.
The Norwegian fortress of Fredriksten in Halden rises over the Iddefjord, and Halden's river Tista has its mouth in the Iddefjord. The Iddefjord was one of several important geological features that enabled Fredriksten Fortress to successfully repel Swedish invasions in 1716, 1718, and 1814.
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