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. The original arc consisted of 258 main triangles with 265 main station points. The listed site includes 34 of the original station points, with different markings, i.e. a drilled hole in rock, iron cross, cairns, or built obelisks.

http://whc.unesco.org/en/list/1187

The Struve Geodetic Arc is a chain of survey triangulations stretching from Hammerfest in Norway to the Black Sea. The chain was established and used by the German-born Russian scientist Friedrich Georg Wilhelm von Struve in the years 1816 to 1855 to establish the exact size and shape of the earth. 

The area of the Arc designated as a WHS consists of 34 stations, spanning 10 countries and over 2,820 km. Originally there were 265 stations, in only 2 countries (the Russian Empire and the Union between Sweden & Norway). 

http://www.worldheritagesite.org/sites/struvegeodeticarc.html

Historic Centre (Old Town) of Tallinn

The origins of Tallinn date back to the 13th century, when a castle was built there by the crusading knights of the Teutonic Order. It developed as a major centre of the Hanseatic League, and its wealth is demonstrated by the opulence of the public buildings (the churches in particular) and the domestic architecture of the merchants' houses, which have survived to a remarkable degree despite the ravages of fire and war in the intervening centuries.

http://whc.unesco.org/en/list/822

The Historic Centre (Old Town) of Tallinn was one of the best fortified cities in Europe, with 66 towers adorning the city wall. Only about 20 of them remain today. Its history as a trading town can still be seen in the wealth of its buildings.

Tallinn, the capital of Estonia, is named after taani linnus, which means Danish castle. The Castle in question was built by King Waldemar of Denmark in the 13th century. The settlement quickly developed itself into a busy port. In 1248 Tallinn became a member of the Hanseatic League, a chain of European trading cities. 

http://www.worldheritagesite.org/sites/tallinn.html