Kärnäkoski Fortress is a bastion fortress in Finland located in Kärnäkoski, Savitaipale built by Russia between 1791 and 1793 to protect Saint Petersburg.
Wikipedia https://en.wikipedia.org/wiki/Kärnäkoski_Fortress
Official Website http://www.partakoskenkylat.fi/fi/matkailu/karnakosken_linnoitus
Address 54800, Finland
Coordinates 61°15'44.131" N 27°42'38.437" E