If you want to choose one point to visit Struve Geodetic Arc the best place is probably the Tartu old observatory. The observatory is located on a hill next to the town centre. Inside of a observatory there was small exhibition about astronomy and 2 very helpful ladies who told about the history of observatory and the geodetic arc. There was big map of the Struve arc and some brochures and sign saying it's world heritage site.

Otherwise Tartu is very lovely town, worth of day trip from Tallinn for example. There's buses (and slow train) going all the time between the cities.

I have also visited the Aavasaksa point of arc in Finnish Lapland long time ago. It's right next to the road between Tornio and Kilpisjärvi and good place to stop on your way to north and see the beautiful views to Tornio River valley.