No idiotic question.
This is a route still travelled by the hugely expensive private train companies that market as 'orient express' experiences. I travelled it buying tickets on ordinary train lines, 2 years ago. It is very straightforward - I took my time over it but to telescope what I did would equal:
Paris Gare du Nord to Vienna - overnight
Vienna to Budapest - couple of hours
Budapest to Bucharest - overnight
Bucharest to Istanbul - overnight
So 3- 4 days total, depending on how to choose to get to Paris. If you are in SE england this is very easy with eurostar, but being in the north I flew to Paris on a budget airline. There is a train from Charles de Gaulle airport directly inot the heart of Paris and in addition, this route puts you directly in the heart of Istanbul at the end. The train goes directly round the outside of the Topkapi Palace, by the Bosphorus. HOWEVER.....the last two legs were at the time I travelled very very taxing on the traveller. The Romanians appeared to have no concept of 'the customer' and we were actually locked into our railway carriage, with filthy communal 'bathroom' and no air con, and a six-inch square of opening window, with temps in the 40s centigrade.
The train was eight hours late into Istanbul, and no refreshments were available on board. We knew this in advance and were prepared with grub and water but the heat and the filth were trying, as well as the carriage attendant who seemed to have trained in the Gulag.
There were numerous border checks, often in the night, by guards who were not used to democracies and seemed to want one to be in awe of them, but that could be said of many folk in uniform the world over.
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