The first exhibit places a mirror and some tridimensional models, representing "a half" of a milanese building, at the visitor's disposal. If you put one of these models to the mirror, you can rebuild the whole building. The image in the mirror and the beginning piece make a building identical to the original... or "almost" identical; quite often symmetry is seeming only, as there are one or more elements that break it and that are evident if you compare the images from life, that are reproduced in one of the exhibition posters, with those in the mirror. The same mirror can be used to look for symmetry in plane figures, such as in some rose windows of the Duomo or in some Roman mosaics of the Ortaglia Domus in Brescia: a slot allows the rose windows image to slide under the mirror and to look for a position where the half image, together with the reflected one, rebuild the whole rose window... or even to admire those figures that reproduce themselves in different positions.

It is possible to make a similar test with two perpendicular mirrors: this time the tridimensional models represent "a quarter" of some buildings, and once again, the whole building, almost identical to the original, could be built by putting those models among mirrors. And in the same way, if you put "a quarter" of a rose window among mirrors, the whole rose window could be built occasionally (sometimes not: it is the visitors' duty to understand when it's happening or it isn't).

Whereas the third exhibit proposes a test looking for another kind of symmetry, which is not realized by means of mirrors: in a specially provided box, let's rotate two copies of the same figure, one upon the other one, to verify when the figure goes back to one's starting point, even before the tour is over. The rose windows of the Duomo together with the Roman mosaics of the Ortaglia Domus in Brescia give the best idea for exploring this possibility again. A "gallery of virtual images" increases the number of available images and allows them to be admired in groups according to their kind of symmetry.

Trying to use three mirrors and a eighth after having employed a ...half monument (and one mirror only) and then a quarter (and two mirrors) to rebuild the whole monument is a natural consequence. It is not easy to find examples of monuments that can be built in this way, because the top and the bottom side should be specular (for instance each door should have a corresponding one on the ceiling): and yet we have found something.

In the course of this part you come across a room whose four walls are mirrors; if you insert a drawing in the provided slot you can observe the result: an extensible floor... "to infinity". In Milan there are many floorings with this symmetry draft and they can be rebuilt in this way, starting from the Duomo floor. It is also possible to find these decorations, that recur at regular intervals with a four mirrors scheme, on the walls of some buildings (for instance some places at the Castello Sforzesco, but even on private homes walls).
However not all decorations are done in this way, of course: some of them need a box of mirrors of different shapes, while some others cannot be rebuilt with mirrors; some posters present many examples and the visitor is invited to recognize "the outsider", that is to say, which is the drawing that you cannot rebuild by means of mirrors. Some interactive animations allow different possibilities to be explored and let the visitor build a mosaic, by means of a mirror room, and then try to recognize the kind of symmetry.

The visitor is invited to go into a large-sized mirror room, to admire the red and white triangle flooring you come across in corso Vittorio Emanuele: the visitor will have to choose the right floor tile, among three types at his/her disposal, to rebuild the flooring reproduced in the photograph.

Friezes, that is to say, drawings that recur at regular intervals in one direction only, are another kind of decorations we often come face to face. Seven posters suggest a collection of examples: they are presented "in groups" according to possible schemes of symmetry (and they are seven, just seven). One of these schemes is just the symmetry scheme of our footprints (for instance on the sand) when we are walking at regular steps; the others too can be illustrated by a sequence of footprints, but it will be necessary to jump to one's feet joined or to hop or move in other acrobatic ways.
Some animations allow the visitor to observe different types of friezes and, furthermore, to recognize types and try to make them by himself/herself using the seven different schemes.