Leonhard Euler and the seven bridges of Konigsberg.
Kalingrad Today The Russian city of Kalingrad is a seaport and lies in a Russian enclave bordering Poland and Lithuania. In the eighteenth century this city was in the Prussian empire and known as Konigsberg. This city was founded in 1254 by a group of Teutonic knights under the order of King Ottoker II. After the Second World War, it came under Soviet rule and was renamed after Michael Kalinin one of the heroes of the Russian Revolution. Konigsberg had a special geographic peculiarity. It lay on 4 separate landmasses, two of which were islands and the other two the banks of the River Pregel. One of the islands, Kniephof lay at the junction of Pregel and the Pregolya river. During the heyday of the Prussian empire, the four landmasses were connected by 7 bridges. These bridges were named the Blacksmith’s bridge, Connecting Bridge, Green Bridge, Merchant’s Bridge, Wooden Bridge and High Bridge. The outer landmasses were connected by 3 bridges each, while the central ...