The arch stands proud of the rubble supporting walls, and is decorated with a modillion cornice.
From the en.wikipedia.org
A cornice runs above the top floor, but is not continuous and changes in style from flat to modillion.
From the en.wikipedia.org
In the Roman Doric order the mutule was horizontal, with sometimes a crowning fillet, so that it virtually fulfilled the purpose of the modillion in the Corinthian cornice.
From the en.wikipedia.org
More examples
(architecture) one of a set of ornamental brackets under a cornice
This page is a glossary of architecture.
A decoratively carved supporting block atop a column
(modillions) Ornamental blocks or brackets used to support the corona in the Corinthian orders
A projecting scroll-shaped bracket or simple horizontal block arranged in series under the soffit of a cornice.
Decorated blocks or brackets placed below a cornice.
Bracket under the cornice in a Classical entablature.
Enriched block or horizontal bracket generally found under the cornice and above the bedmold of the Corinthian entablature. It is probably so called because of its arrangement in regulated distances.
A small bracket used in rows under the corona of a cornice and extending from the bed mold. It frequently takes the shape of an ornamental double volute.