In 1831 Mr. Franzen, the owner of the Salahmi Ironworks was given permission to establish a blast furnace and a bar-iron forge at Jyrkkäkoski. The early years were difficult, because Jyrkkäkoski was not at any close distance of main travel routes and sufficient labour was not available. In 1856, the ironworks was obtained by Paul Wahl & Co. as part of a larger consortium. A new Scottish-type blast furnace of English brick was erected at the site in 1874.
The ironworks produced pig and bar iron, as well as nails and cast products. In the early 1900s the Ironworks even had its own small steam boat. Many prominent cultural figures were seen at Jyrkkä, including the author Juhani Aho who courted the beautiful daughter of Brax, the manager of the works. The Jyrkkäkoski Works was in operation unti1 1919.
Finland’s National Board of Antiquities carried out conservation and reconstruction works at Jyrkkäkoski in 1996-98. The old ironworks has become an architectural attraction in North Savo. The blast furnaces now have impressive protective structures. In connection with the Scottish blast furnace is Ruukintupa, a cafeteria serving snacks. "Herrala", the manager’s residence dates from the 1830s and the log buildings in the yard area are even older.
Reference: Sonkajärvi Municipality
Ängsö Castle was first named as "Engsev" in a royal charter by king Canute I of Sweden (r. 1167-1196), in which he stated that he had inherited the property after his father Eric IX of Sweden. Until 1272, it was owned by the Riseberga Abbey, and then taken over by Gregers Birgersson.
From 1475 until 1710, it was owned by the Sparre family. The current castle was built as a fortress by riksråd Bengt Fadersson Sparre in the 1480s. In 1522, Ängsö Castle was taken after a siege by king Gustav Vasa, since its owner, Fadersson's son Knut Bengtsson, sided with Christian II of Denmark. However, in 1538 it was given by the king to Bengtsson's daughter Hillevi Knutsdotter, who was married to Arvid Trolle.
In 1710, the castle was taken over by Carl Piper and Christina Piper. Ängsö Castle was owned by the Piper family from 1710 until 1971, and is now owned by the Westmanna foundation. The castle building itself was made into a museum in 1959 and was made a listed building in 1965. It is currently opened to visitors during the summers.
The castle is a cubical building in four stores made by stone and bricks. The lower parts is preserved from the middle ages. It was redecorated and expanded in the 1630s. The 4th storey as well as the roof is from the expansion of Carl Hårleman from 1740-41. It gained its current appearance in the 1740s.