20 Roubles Struve Geodetic Arc

The Struve Geodetic Arc was a chain of survey triangulations stretching from Hammerfest in Norway to the Black Sea, completed between 1816 and 1855 under the direction of Friedrich Georg Wilhelm Struve at Dorpat (now Tartu) Observatory. The survey established, for the first time with genuine precision, the exact shape and size of the Earth along a meridian arc of over 2,820 kilometres. Belarus hosts several of the original benchmark stations, which gave the National Bank its geographic claim to the subject.

UNESCO inscribed the Arc as a World Heritage Site in 2005 — one year before this coin's issue date, which was almost certainly the occasion for the release.