I do love a good mosaic, and I have a particular soft spot for this one from Saint-Romain-en-Gal (Ancient Vienne), approximately 75km to the north-west of Grenoble. In its heyday, it would have adorned a wealthy house and dates to the second century AD. The panel is just over 1m square, and the alternating grey and white borders lead the viewer’s eye to a composition of two birds perched on either side of a two-handled vase (krater) with a jet of water erupting between them. Everything about this composition screams symmetry – two handles, two birds in mirror image, the same number of water streams falling one either side of the central pillar. However, it doesn’t quite work as the main jet of water – that should act as a line of symmetry – is offset ever so slightly (but noticeably) to the right. It simultaneously causes an itch somewhere deep inside my brain while still making me love it all the more.