Editor’s Note: Sign up for Unlocking the World, CNN Travel’s weekly newsletter. Get news about destinations opening, inspiration for future adventures, plus the latest in aviation, food and drink, where to stay and other travel developments. CNN  —  It was “Rail Force One” – the overnight train that took US President Biden on a diplomatic odyssey from Przemyśl Główny in Poland to Kyiv for his historic visit to Ukraine, just before the first anniversary of Russia’s invasion of the country. The 10-hour overnight journey was a top secret, high security challenge for Ukrzaliznytsia, or Ukrainian Railways – the state-owned operator of Ukraine’s rail network. But it was hardly their first.…