Châteaugiron developed around its château from the 13th century onwards, becoming more prosperous towards the end of the Middle Ages as the canvas sail industry expanded. The town’s unique historic town centre is very well-preserved and features significant remains of the medieval fortress, renovated between 1450 and 1470 by Jean de Derval. Of the six original towers, four are still standing: the 38 metre high 13th-15th century keep, built independently of the château, the 14th-15th century clock tower, a belfry during the French Ancien Regime, and the 15th century watchtower and Cardinal’s tower, whose elevated patrol paths with machicolation projections has been preserved.References:
Frösöstenen is the northern-most raised runestone in the world and Jämtland's only runestone. It originally stood at the tip of ferry terminal on the sound between the island of Frösön and Östersund. The stone dates to between 1030 and 1050. It has now been relocated to the lawn in front of the local county seat due to the construction of a new bridge, between 1969 and 1971, on the original site.
Frösö runestone inscription means: Austmaðr, Guðfastr's son, had this stone raised and this bridge built and Christianized Jämtland. Ásbjörn built the bridge. Trjónn and Steinn carved these runes.