The Suomenlinna sea fortress is part of Finland's national cultural heritage and a valuable monument. Suomenlinna has been inscribed on the UNESCO World Heritage List to be preserved for future generations as an example of the European fortification architecture of its time. Its historical significance in the defence of three separate states - Sweden, Russia and Finland - gives the fortress its own special importance. Suomenlinna is today a lively city district and one of Finland's most popular tourist attractions.