Finland was part of Sweden for almost 700 years from around 1150 until the Finnish War of 1809 after which Finland became an autonomous part of the Russian Empire as the Grand Duchy of Finland.
Here is a list of some of the most well-preserved castles in Finland.
Sveaborg
Åbo
Tavastehus
Raseborg
Cecil, Wikipedia
Kastellholm
Olofsborg
