Every time I visit a new European country or city, I love to go to museums and galleries. I've been to some boring ones but I usually come out with more knowledge and interest in an area than I did before!
My personal favourites are,
1) Dachau concentration camp – Dachau, Germany
2) War Childhood Museum – Sarajevo, Bosnia and Herzegovina
3) The Louvre – Paris, France
4) Memorial to the Abolition of Slavery – Nantes, France
5) Pinacoteca di Brera – Milan, Italy
Let me know what your favourites are!