Bridges of Königsberg/Historical Note

Historical Note on Bridges of Königsberg
The solution of the Bridges of Königsberg problem, in a rather different form, was first given by in his $1736$ paper Solutio problematis ad geometriam situs pertinentis.

This is widely considered as the first ever paper in the field of graph theory.

Mathematically-minded tourists are to be aware that the City of Königsberg is currently a part of Russia, and goes by the name of Kaliningrad.

It is very much not the same as it was. There are now only five bridges, and their configuration corresponds to a graph which is now semi-Eulerian.

Like many places that were taken over by Russia in the 20th century, it has been allowed to deteriorate.