Here you can see a photo completely symmetrical. If we divide
the picture horizontally in 2 planes, they will be the same. And
if we divide the picture vertically in 2 planes, they will also
be equal. For the picture is symmetrical objects in each level
are not necessarily identical. The photo below is symmetric
because the elements in the picture, although not identical, are
sufficiently similar and have the same visual weight to look
like objects.