Gammelstad, at the head of the Gulf of Bothnia, is the best-preserved example of a 'church village', a unique kind of village formerly found throughout northern Scandinavia. The 424 wooden houses, huddled round the early 15th-century stone church, were used only on Sundays and at religious festivals to house worshippers from the surrounding countryside who could not return home the same day because of the distance and difficult travelling conditions.

Źródło: World Heritage Convention
http://whc.unesco.org/en/list/762