History of the Peloponnesian War

It was by his advice, too, that they built the walls of that thickness which can still be discerned round Piraeus, the stones being brought up by two wagons meeting each other. Between the walls thus formed there was neither rubble nor mortar, but great stones hewn square and fitted together, cramped to each other on the outside with iron and lead. About half the height that he intended was finished.

His idea was by their size and thickness to keep off the attacks of an enemy; he thought that they might be adequately defended by a small garrison of invalids, and the rest be freed for service in the fleet.