Claustra (claustra ©)

The translation in the title is followed by this sign ©; this means that it has been "invented" by me.

A number of ajouré (ajoure) tiles closing off a baie (opening).
In Rome I stumbled upon an impressive collection of claustras in the Basilica di Santa Sabina.
In my own collection I also found some of these tiles which have been used as decoration in the walls of one of the chapelles (chapels) of the Saint-Philibert in Tournus.

Basilica di Santa Sabina - Rome

Saint-Philibert in Tournus