Because the original train connection is no longer there, one has to choose from the different routes the train followed between 1883 en 1977. The hiking trail will more or less follow the route of the timetable of the train from 1885 between Paris en Varna in Bulgaria (the oldest west-east connection). From Varna (
Below details of the route in the various countries, including a roadmap of how to further develop the route. The route from Vienna to Varna will probably involve a lot of pioneering, while the stretch from Paris to Vienna will be able to use a lot of existing hiking trails.