various and numerous history books and travel brochures (when they were around) to see places including specific history museums and sites in Germany....
Berlin, Lüneburg, Pinneberg bei Hamburg, Weimar, Wiesbaden, Ratingen, Rüdesheim am Rhein, Hannover, Wustrau/Brandenburg,
Sigmaringen an der Donau, Münster/Westf., Friedrichsruh bei Hamburg, Wesel am Rhein, Duisburg, Rastatt, Munich, Kelheim,
Potsdam, Marburg an der Lahn, Minden an der Weser, etc, etc.
After reading the books to see the Napoleon sites...Paris, Toulon, Montmirail, Leipzig, Boulogne sur Mer, Fontainebleau, Malmaison, Austerlitz (Slavkov), and obviously, Waterloo,