... in South Finland near to the Hanko peninsula.
You can easy get the Line by train from Helsinki city with change in Karjaa. Way from Helsinki to Karja will last for an hour, from Karja to Skogby - near to 20 min. Free time in Karja you can spent to see the historical locomotive. Local people say that great Russian leader V.I.Lenin worked as stoker on this train and earn money for proletarian revolution. By the way, there are good many such a locomotives in Finland.
Nearest bunker is 200 meters from Skogby railway station. The area has dimensions near to 4x4 kilometers with more than 30 defence installations, so you will have a busy day. Huvä paivää!