Halden sits at the innermost end of a narrow fjord arm right on the Swedish border, and its whole identity is shaped by that position. King Frederik III founded the town in 1665 as Fredrikshald, built to hold the border after Sweden had seized the province of Bohuslän to the south. It kept that name until 1928, when it reverted to the older Halden.
The reason to come is Fredriksten Fortress, the star-shaped stronghold that stands on a rocky hilltop directly above the town. It withstood repeated Swedish sieges through the 17th and 18th centuries — the town motto, "Never conquered," commemorates that record — but it was here, during the 1718 siege, that the Swedish king Charles XII was shot dead in the trenches below the walls, a death still argued over by historians (accident, or a shot from his own side). The fortress grounds are open and free to wander, with sweeping views over the town, the fjord, and the border hills into Sweden.
Below the fortress, the town itself is compact and pleasant, its centre built around the harbour where the Tista river meets the fjord. A short way out, Rød Herregård is a well-preserved 18th-century manor house that belonged to a timber-trading family, furnished much as it would have been in its Georgian-style prime. Further afield, the Halden Canal — a 19th-century timber-floating waterway with a working set of locks at Brekke — threads north into the forested lake country behind the town.
Halden works well as a day trip from Fredrikstad, 35 km north, or as a stop on the way to or from Sweden.