The Struve Arc measurement point Oravivuori is the most famous of the points located in Finland. Oravivuori is situated in Korpilahti in central Finland, which is now part of the city of Jyväskylä. The drive south from the center of Jyväskylä is about forty kilometers, with the remaining part of the route being a narrow dirt road. Near it, about a kilometer’s walk from the top of Oravivuori hill, there is a small parking lot. From there begins a steep climb along a clearly marked rocky trail. Along the route, there are also several signposts. In the wettest places, short wooden walkways help, and closer to the end of the route, you ascend wooden steps.

The total ascent is about 90 meters. At the top of Oravivuori, which is 193 meters high, a wooden observation tower has been erected, offering a breathtaking view of Päijänne. This tower, rebuilt in 1997, serves as a reminder of the history of geodesy, since during the Golden Age of triangulation there were many similar towers throughout Finland. The actual Struve point is marked by a hole drilled into the rock in 1834. Struve used the name Puolakka from the Oravivuori cape.

The Struve Arc, once known as the “Russian” and then the “Russian-Scandinavian Meridian Arc,” is one of UNESCO’s World Heritage monuments. The Arc consists of 265 triangulation points, along which measurements were conducted from 1816 to 1852 that allowed the precise determination of the size and shape of the Earth.

The reference points of this triangulation network were marked on the ground in various ways: depressions carved into rocks, iron crosses, stone pyramids, or specially erected obelisks. Often they were marked with sandstone bricks placed at the bottom of a pit; sometimes it was a granite cube with a cavity filled with lead, placed in a pit with cobblestones.

During the project to include the Struve Arc in the UNESCO list, which lasted 8 years, special search and geodetic work was carried out in each country to locate the original points. All information from all the Struve Arc countries was collected, structured, and standardized.

Not all of the original points were found during the special search and geodetic work carried out in recent years with active cooperation from scientists of the interested countries, and moreover, many of them were found to be heavily damaged. Therefore, only the best-preserved points—34 in total—were included in the World Heritage site.

Sources:

http://www.gototrip.com/publications/geodezicheskaya-duga-struve

https://visitmeri-lappi.fi/nae-koe/kulttuuri/unescon-maailman-perintokohde/