Salpa Line defence line steel and concrete bunker in Puumala is a Saimaa Geopark’s natural and cultural site. Salpa Line (Salpalinja) is a 1,200 km defence line that was built in 1940, 1941 and 1944 to defend the eastern border of Finland. Salpa Line defence bunker in Puumala was built in 1941 and it can accommodate 20 soldiers.