The map makes it look cheap to add a second country. A budget airline, a night train, a border that does not stamp. What you actually add is another airport hour, another first dinner, and a morning you spend checking out instead of walking.
Italy is already several older countries sharing a railway. Greece is a mainland and a ferry timetable. Australia is a continent with a handful of coastal cities. None of these need a neighbour stacked on top to feel like a trip.
If you have a week, pick one country and one other region inside it. The second stamp can wait until you have sat still long enough to know what you would actually go back for.
