Will definitely check this out. Our go-to guide whenever travelling Europe has always been Rick Steve's books and audio guide app. Those are like having a personal guide with you as he will tell cool things like "take few steps to the left, now the point you are standing is where Hitler stood and made a painting of this church (in Vienna)" or "Leonardo da Vinci used to stare at this artistic metal door for inspiration (in Florence)". Those audio tours are one of the most fun things we remember from our trips as he is a great storyteller.