Cave in WW1 base, Kivikko, Helsinki, Finland

Unfinished 170 m2 U-shaped cave in First World War base IV:6 in [Krepost Sveaborg](https://en.wikipedia.org/wiki/Krepost_Sveaborg) land front defense line in Kivikko, Helsinki, Finland. The base was built in 1915 - 1918. More info: * [Location in Google Maps](https://goo.gl/maps/3HRbxufygFctc4Uc7) * [Wikipedia: Krepost Sveaborg](https://en.wikipedia.org/wiki/Krepost_Sveaborg) * [John Lagerstedt , Markku Saari: Krepost Sveaborg](http://www.novision.fi/viapori/eavaus.htm) * [Finnish Heritage Agency site info](https://www.kyppi.fi/to.aspx?id=112.1000011233) (only in finnish)