A short walk from the AHHAA Science Centre stands the Tartu Old Observatory. Building was completed in 1812 and it is now a UNESCO World Heritage Centre as part of the 2,800 km long Struve Geodetic Arc.
"The Struve Arc is a chain of survey triangulations stretching from Hammerfest in Norway to the Black Sea, through 10 countries and over 2,820 km. These are points of a survey, carried out between 1816 and 1855 by the astronomer Friedrich Georg Wilhelm Struve, which represented the first accurate measuring of a long segment of a meridian. This helped to establish the exact size and shape of the planet and marked an important step in the development of earth sciences and topographic mapping. It is an extraordinary example of scientific collaboration among scientists from different countries, and of collaboration between monarchs for a scientific cause." [UNESCO World Heritage List]