Turku castle in Turku / Åbo (Swedish), Finland. (Photographer unknown). A start was made on building the castle in about 1280. The castle served as a bastion and administrative centre in Eastland, as Finland was known during its time as a province of Sweden. Only once did the castle figure in the defence of the realm, when Russian invaders from Novgorod destroyed Turku in 1318. The castle's heyday was in the mid-16th century during the reign of Duke John of Finland and Catherine Jagellon.

The castle was the center of the historical province of Finland Proper, and the administrative center of all of Finland. Its strong walls and dungeons also served as the state prison for centuries. The castle has been the place of many historical events; in 1573–1577, for example, the deposed Swedish queen Karin Månsdotter was kept prisoner here.

The castle is Finland's most visited museum. (Source: Wikipedia)