coat of arms of vatican city

Stemma, muro della Città del Vaticano, 2009.

The papal insignia are at the top of this coat of arms which features six fleur-de-lis, a symbol usually associated with France. I know almost nothing about heraldry, so I am unable to identify the shield. The carved stone is at a corner of the wall which surrounds part of Vatican City and separates it from Rome (the SPQR on the side shields).