This museum covers the history of Jews in Prague (and not only) and is a must-have when being in Prague. Although the admission is quite pricy, it's definitely worth the price. The best option is to buy a ticket allowing you to visit all the places that the museum consists of, i.e.: five synagogues, Old Jewish Cemetery and the Ceremonial Hall. The Old-New Synagogue is still in use but open for visitors. At least 4 hours are needed for the museum, although the ticket suggests three with detailed times for each place (which don't have to be obeyed, contrary to what is written on the ticket).