Hi, MustangGal: I am originally from NY (Manhattan). Your nieces are very lucky to have such a doting Aunt. Europe is a fascinating continent to visit and the railway system is the best way to go about because each city is almost just a hop, skip and a jump from each other. Paris is only a 3 hour journey by train from London. You can pick a port of entry in any European city and venture onwards from there. Travel by rail also allows the traveller to have a better insight of each country and its people. If you plan your journey well, you can cross the continent from Rome to London (or even the opposite direction) by rail in two months and manage to visit countries in-between along the way. Your nieces surely have a treat to look forward to.