Before the Finnish winter war, Finland had built up a line of defence (Mannerheimlinjen) that crossed the Karelian nose as a defence against the Soviet Union. After the peace of March 1940, this line of defence lay in the Soviet Union and Finland began a new construction of a line of defence under what has been called the middle peace (the time between the Finnish winter war and the continuing war). The line was called the Salpa line and is located about 200 kilometres east of Helsinki and was a 1200 kilometres line of defence that ran from southern to northern Finland. However, the Salpa line was never used during the continuation war because Finland surrendered before the fighting reached the line.

Current status: Preserved with museum (2009).

Location: 60°41'03.8"N 27°40'16.5"E

Get there: Car.

My comment:

Mannerheimlinjen is nowadays loctaed in Russia and there are remains of it but there are to my knowledge no museums in place. Although there were never any battles at the Salpa Line, it is interesting to wander around among the defensive positions.

Follow up in books: Trotter, R William: The Russo-Finnish Winter War of 1939-1940 (2010).