This short article is about our Giessener Mathematikum, a hands-on minds-on science centre which is unique in the world as an institution solely directed to reaching out to the general public in order to show that mathematics is an interesting and enjoyable subject for everybody. Given many unjustified prejudices against this subject from lay people, it was a challenge to create a large science centre that is attractive to everybody and aims to convince that the beauty, depth and usefulness of mathematics is comprehensible to all, independent of a particular education and particular scientific inclination. We believe we have succeeded, and my purpose is to outline the history and present operation of the Mathematikum, and its various ways of meeting the mentioned challenge.