Arc à double rouleau (double arch ©)

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

This is an arc (arch) consisting of two rows of stones placed above each other.
In the photograph the nef (nave) of the Saint-Philibert in Tournus.
See also double rouleau (synonym).

Saint-Philibert - Tournus