Rather than one building, the Jewish Museum is a collection of sites around the Jewish Quarter in Prague. You can buy tickets individually for each or buy a combi-ticket that admits you to all of them. The great thing about the combi-ticket is that you don't need to see them all in one day so you can take it at a gentle pace. The Jewish Cemetery is by far the most popular of the sites so aim to visit at a quieter time. The Spanish Synagogue is architecturally impressive and the Maisel Synagogue has a great museum inside. There aren't many food or drink options in the immediate area so wander back towards the Old Town Square if you get hungry.