The ancient walls of Avila, constructed of brown granite, and surmounted by a breastwork, with eighty-six towers and nine gateways, are still in excellent repair; but a large part of the city lies beyond their circuit.
On the east and west the ravines already mentioned afforded, in the main, a sufficient protection, so that a massive wall was unnecessary, while near the south-eastern angle a breastwork was formed by the excavation of the natural rock, 2 which in later times was honeycombed with tombs.
The walls are embanking walls, with a low breastwork in places.
Not only was the wall of Anthemius restored, but, at the distance of 20 yds., another wall was built in front of it, and at the same distance from this second wall a broad moat was constructed with a breastwork along its inner edge.
A low timber breastwork prevents landward migration of spit onto marshes.