Pro restauratione murorum huius excellentissime urbis. Le Mura Aureliane di Roma nel Basso Medioevo
The Aurelian Walls of Rome had extensive late medieval renovations. The constant characteristics of these restorations are the irregular arrangement of the stones of the outer layers ('flint', tuff, peperino, travertine, fragments of marble and brick) and the frequent presence of partial horizontal rows of brick. The mortars are lime and sand, almost all without pozzolana. This type of masonry is not rare in the Roman area, mainly in fortified buildings, dating back to the same centuries.