This is a map of old-time Kongsberg. The green shapes are bridges which connect the different parts of the city. Can you find a path through the city which goes through every bridge exactly once?
No, you cannot. Notice that, except for the first city and the last city section you finish, the number of bridges used in every other section is even. However, there are three sections with an odd number of bridges, and therefore you cannot use all bridges exactly once.