Following Euler in Koenigsberg

     The Köenigsberg Bridges have an important link to mathematics -- for mathematician Leonhard Euler (1707-1783) took a legendary Köenigsberg puzzle-pastime as the seed for development of a new branch of mathematics, graph theory (which is now generally included under the umbrella of combinatorics).  As the story goes, Köenigsberg residents made a Sunday recreation of trying to tour their city, crossing each of its seven bridges exactly once.  This problem is perhaps particularly fascinating because of its impossibility -- a dilemma cause by the existence of odd (rather than even) numbers of bridges between the parts of this water-separated city.