We did a 1 hour tour of the Jewish Synagogue.  The tour guide was not the most interesting.  However, we did learn some interesting things about the Jewish community in Dubrovnik.  There are only 50 Jews left.  At the height, there were only 250.  The were many beautiful relics in the museum down below.  Recommendation would be not to do the $15/pp tour, but rather just pay the $3 and get into the synagogue on your own.