Highly recommended
This museum offers a thorough overview of the history of the city of Krakow. It's not difficult to find, next to the Moka Contemporary Art museum. Entry costs 19 zloty, but it's free on Mondays. Inside you'll find rooms full of history and emotions, with photographs, videos (you can view them in English), and documents. The tour shows exhibitions, reenactments, and photos (some really hard to look at) which will show you all about the hard times that the Jews in this city had to live through.
In the first part of the visit you can learn about the First World War, and then onto the Second, with the sounds of bombs and sirens.