How triangles measured the Earth

On top of Oravivuori in Jyväskylä sits a concrete cube which doesn't seem much to an everyman, However, it is part of the story on how both Finland and the planet Earth were mapped.
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Käy kurkkaamassa myös musiikki- ja taidekanavani Eroosio:
/ eroosio
Visit also my music and short film channel Eroosio:
/ eroosio