Ruins of Kuusisto Bishop's Castle.
https://en.wikipedia.org/wiki/Kuusisto_Castle
The castle was one of the largest medieval castles in Finland that acted as the catholic bishop's seat. It was (more or less peacefully) demolished by the order of the king during reformation 1528.
Following reuse of materials further diminished the structure further.
An excuisitively beautiful site never the less. The medieval brickwork can still be admired even though only a fraction of the structure remains erect.
The site is now maintained by the Office of National Parks https://www.nationalparks.fi/kuusisto