Kärnäkoski Fortress built
1791 CE.
Shown on the map at 61.260°, 27.710°.
Kärnäkoski Fortress is a bastion fortress in Finland located in Kärnäkoski, Savitaipale built by Russia between 1791 and 1793 to protect Saint Petersburg.
Text from the Wikipedia article Kärnäkoski Fortress, licensed CC BY-SA 4.0.