This is the best of the museum tours if you like modern design, the stuff is just great. Located right across from Marshall Tito Square. I got it on the right day and the admission was free, but the standard is only 20 kuna ($4.00)
My only advice, they have some great design posters in the place. I like posters to show where i have been, it is an inexpensive way to show the trip and to decorate walls. None of their posters were for sale :( and there were some great ones that announced museum events.