Today (19 July) is the 150th anniversary of the start of what the French call the War of 1870
https://en.wikipedia.org/wiki/Franco-Prussian_War
which set the stage for the end of the 2nd Empire and the start of the 3rd Republic,
and also put in place the main rivalries that ran up to WWI ---
Bismarck had been looking for a final motivation to get the German states to unify under him/Prussia,
and taunting Napoleon III into declaring war did the trick, leading to the formation of the German Empire,
and the defeat/delay of the spread of modern liberalism in Europe.
What are the best memorial sites or events to learn more about how the rise of a unified Germany and the end of the 2nd French Empire shaped the world we live in today?
(Edited to make it more directly travel-related)